Whole Class Instruction

Whole class instruction is characterized by the utilization of a traditional, textbook-dominated curriculum (Bagley, 1931; Goodlad, 1984; Reis et al., 1993), movement through the curriculum at the same pace using the same methods and materials (Cuban, 1984; Goodlad, 1984), and instruction for the entire class at the same time (Good & Brophy, 1994).

According to Archambault et al. (1993), classroom teaching has not evolved much from its infancy early last century. Teachers still follow a lockstep curriculum with traditional gradelevel divisions, subject-matter divisions of classroom time and resources, and a sequential model that has the teacher introducing a new lesson, followed in rapid succession by recitation or group practice, additional seatwork, and finally, homework to allow students to practice the skill on their own (Good & Brophy, 1994). Goodlad (1984) observed that "a great deal of what goes on in the classroom is like painting-by-the numbers — filling in the colors called for by numbers on the page" (p. 108).

In Goodlad's seminal study of America's classrooms (1984), he mused about the role of the teacher in the classroom. "No matter how we approach the classroom in an effort to describe and understand what goes on, the teacher comes through as coach, quarterback, referee, and even rule-maker. But there the analogy must stop because there is no team" (p. 108). He observed that the teacher made virtually all of the choices in the classroom, including what questions to ask and which to answer. According to Goodlad, "the didactics of the classroom are very much the same from school to school; teachers lectured and questioned, students listened, [and] textbooks were the most common medium for teaching and learning — there was much pedagogical conformity" (p. 247).

Teacher- versus student-centered classrooms. Cuban (1984) described the observable characteristics of classrooms as either teacher- or student-centered. Teacher-centered classrooms are characterized by teacher talk that exceeds student talk during instruction; instruction that occurs mainly in a whole-class setting with small group or individual instruction occurring less frequently; teacher determination of class time; and a classroom arrangement that typically includes desks that are arranged in rows, facing the blackboard, with a teacher's desk nearby.

In teacher-centered classrooms, teachers ask questions for which there is only one right answer, while imploring students to become more independent thinkers and learners (Goodlad, Soder. & Sorotnik, 1990). Adams and Biddle (1970) noted that the teacher is the principal actor in 84% of classroom communication and Cuban (1984) noted that classrooms are characterized by a heavy reliance on teacher-initiated drill and recitation. Even when students are placed into small groups, they are frequently working on the same activities and lessons (Cuban; Good & Brophy, 1994; Goodlad, 1984; Kulik & Kulik, 1992). Student-centered classrooms are characterized by student talk on learning tasks at least equal to teacher talk; instruction that occurs mainly in small groups or individually; students' needs are infused into the organization of content to be learned; students help determine rules of behavior and enforcement: use of varied instructional materials that can be used by individuals or by students within small groups; students use materials organized by the teacher or determined by the students at least half of the time; and the classroom is organized to allow students to move independently within their work space, including the physical movement of desks and chairs to facilitate instruction.

The major advantage of whole group instruction is that more students can be educated within a graded classroom in which the teacher prepares lessons based on a single ability or readiness level (Goodlad, 1984). The major disadvantage is that students move through the curriculum without regard to their prior knowledge, interests, or levels of readiness (Good & Power, 1976). This practice has been the dominant grouping arrangement since the mass industrialization of the American economy in the late eighteenth century (Grinder & Nelsen, 1985) and continues to dominate the educational landscape today (Archambault et al., 1993; Cuban, 1984; Gardner, 1999; Good & Brophy, 1994; Goodlad, 1984).

Between-Class Grouping

The best known of the between-class grouping plans is the Joplin Plan, devised by Cecil Floyd, the assistant superintendent of schools in Joplin, Missouri (Floyd, 1954). The earliest version of this plan included the cross-grade grouping of elementary students in reading. During the time reserved for reading, students in grades 4, 5, and 6 would proceed to different classrooms to receive instruction geared to their readiness levels. Students in the high group would use textbooks from grades 6. 7, and 8; students in the middle group would use textbooks from grade 5, 6, and 7; and students in the low group would use textbooks from grades, 4, 5, and 6 (Kulik, 1992). After the hour was over, students would return to their regular classrooms. This grouping arrangement was later expanded to include arithmetic instruction.

The Joplin Plan. There are three major advantages to the Joplin Plan grouping arrangement. The first advantage is the temporary nature of the grouping arrangement. Most modern cross-grade grouping plans are single-subject oriented and closely tied to a specific skill. This arrangement allows students to move into and out of groups based on their current demonstrated achievement (Kulik & Kulik, 1982; Slavin, 1987). Students are preassessed in one or two subjects and grouped according to their actual performance in these areas. Students generally attend another classroom for instruction in reading or mathematics then return to their regular classroom or homeroom for the remainder of the school day. According to Slavin, regrouping for instruction (Joplin Plan) allows errors in original student placement to be remedied without moving students to another class section or changing their basic homeroom assignments.

A second major advantage of the Joplin Plan is the curricular adjustment made among groups. The teacher must develop curriculum according to the unique needs of the group, rather than utilize a "one size fits all" approach to curriculum development. Students use textbooks from different grades based on their level of readiness (Kulik. 1992). According to Kulik and Kulik (1992), students in different ability groups work with different materials and different methods. Hence, the match between grouping arrangement and curriculum is enhanced.

A third major advantage of between-class, cross-grade grouping plans is the admirable goal of reducing heterogeneity in the classroom without adversely affecting the self-esteem of those students in the lowest achieving groups (Begle, 1975: Goodlad, 1966: Slavin, 1987). Goodlad suggested that the spread in "average achievement in an elementary-school class slightly exceeds the number of the grade level" (p. 6). This means that in the typical fourth grade classroom, there are students who are working at the second grade as well as sixth grade levels. "A teacher who says, 'I teach the fourth grade,' is talking about only three or four children in the class!" (Goodlad, p. 6). Goodlad further suggested that standardized tests most likely would fail to note the distinction between two average fourth grade students: one who scores 3.9 grade equivalents in arithmetic computation and 7.4 in paragraph meaning and another who scores 6.7 in arithmetic concepts and 3.2 in vocabulary and reading comprehension. By regrouping for a single subject, teachers are more likely to reduce the heterogeneity within the classroom, while assuring that they are meeting the appropriate curricular needs of each student.

Within-Class Grouping

A third major type of grouping arrangement is within-class or flexible grouping (Benbow, 1998; Davis & Rimm, 1994; Peldhusen & Moon. 1992; Kulik. 1992; Kulik, 2003: Renzulli 1994; Slavin, 1987; Tomlinson, 1995, 1999; Westberg & Archambault, 1995). This practice groups students within the same class into "smaller groups for specific activities and purposes" (Kulik & Kulik, 1992, p. 75). Typically, the teacher presents a lesson to the whole class and then places students into small groups based on demonstrated performance, interests, levels of prior knowledge, and the like. (Renzulli, 1994). Kulik and Kulik identified several facts about within-class grouping plans. First, for within-class grouping practices to be successful, teachers must differentiate instruction. It would not be an expedient use of resources and time to preassess students, place them into small groups, and make the same presentation to two or three separate groups. Second, students should remain within their regular classrooms for the entire school day. This plan can alleviate the potential scheduling problem of having all teachers teaching the same subject at the same time. According to Slavin (1987), the major advantage of flexible grouping is the temporary nature of the groups. Students are assessed frequently for growth and reassigned to different groups based on that assessment.

Within-class grouping and W opportunity to learn. Sorenson and Hallinan (1986) suggested that one of the key issues underlying the debate over ability grouping is students' opportunity to learn. They proposed that students' ability and effort determine how they utilize opportunities for learning provided by the teacher. Within the framework of that model, they suggested two benefits to students of within-class ability grouping. First, teachers have an easier time obtaining and retaining students' attention when there are fewer of them in the instructional group. Second, teachers are more able to adapt their methods of instruction and instructional materials to students within a smaller, more homogeneous group. Even though instructional time is actually diminished when students are placed into small groups, the amount and type of learning that occurs in these small groups more than compensates for the shortened instructional time. Sorensen and Hallinan summarized that "the increased attention and the adaptation of the instructional materials to the aptitudes and preparation of students should help students make better use of their abilities. This grouping might result in students making more efficient use of their intellectual resources" (p. 522). Even though there are demonstrated advantages in the use of within-class grouping, there are also consequent problems.

A major disadvantage of within-class grouping is that teachers are required to learn a new form of classroom management to create a learning environment sensitive to individual levels of readiness and manageable in terms of student behavior (Arlin, 1982; Tomlinson, 1999). Due to this concern about classroom management, many teachers who attempt to utilize different learning tasks for different small groups concentrate on extensive drill and practice, especially for students with lower levels of readiness. Though this drill and practice approach may facilitate classroom management, it deprives students of the opportunity to work with higher-level concepts, resources, and methodologies (Newman & Schwager, 1992). Kulik and Kulik (1992) suggested that when within-class grouping is successful, teachers differentiate instruction for the different groups and students remain within their regular classroom. Students placed into different groups based on their levels of readiness should all be engaged in work that is meaningful and appropriate for their specific learning needs.

Research on Grouping Practices

Research on ability grouping has continued for almost a century. The earliest recorded study occurred in Salt Lake City, Utah, in 1927 when researchers identified and preassessed two equivalent groups of elementary students (Kulik, 1992). Students in one group were separated by ability and placed into homogeneous classes while students in the other group were assigned to mixed-ability classes. Students were tested again at the end of the school year and those in the homogeneous group scored approximately two grade equivalents higher in mathematics than did similar-ability students in the heterogeneous class. With those results, the opening shot was fired in the century-long battle over the grouping of students for instruction.

In an early summary of ability-grouping practices, Passow (1962) suggested that the results of numerous studies on ability grouping depended less on the "fact of grouping itself than upon the philosophy behind the grouping, the accuracy with which grouping is made for the purposes intended, the differentiations in content, method, and speed, and the technique of the teacher" (p. 284). Kulik (1992) reviewed early studies of research on ability grouping (i.e., 1900's-1950's) and applied meta-analytic techniques (Glass, 1976) to these studies. He found nontrivial average effects (ES = .14) for students grouped for mathematics by ability, without any curricular adjustment, when compared to whole class instruction.

Modern meta-analytic studies suggest that average effect sizes for student achievement in classes grouped according to the Joplin Plan (with curricular adjustment) is .33, a small but nontrivial effect size (Kulik & Kulik, 1982). Kulik and Kulik investigated 16 controlled studies of the Joplin Plan for cross-grade grouping in one or two subjects. Twelve of those studies found higher achievement levels in the Joplin Plan classes. Two Joplin Plan studies reported effect sizes for different ability levels separately. A median effect size of .12 was reported for the high achieving group, — .01 for the middle group, and .29 for the low achieving group (Kulik & Kulik). Slavin (1987) found a median effect size of .45 for Joplin Plan grouping, while Rogers (1991) noted average effect sizes of .34. Additionally, Mills, Ablard, and Gustin (1994) found large effect sizes (ES = 2.4 SD) for fifth graders enrolled in a Joplin-like, flexibly-paced mathematics course with appropriate curricular adjustment.

Finally, Slavin (1987) found significant, moderate effect sizes (ES = .41) and Kulik (1992) small average effect sizes (ES = .25) for within-class (flexible) grouping. Nine of Kulik's eleven studies reported higher overall achievement levels with flexible grouping arrangements (average ES = .25) over whole class instruction. Lou et al. (1996) found average effect sizes of +.17 in a meta-analysis of within-class grouping versus no grouping. In comparisons of heterogeneous versus homogeneous within-class grouping, they found average effect sizes of +. 12 for homogeneous grouping. Slavin argued that research on within-class grouping in mathematics "consistently supports this practice in upper elementary grades" (p. 320). He also contends that "there is no evidence to suggest that achievement gains due to within-class ability grouping in mathematics are achieved at the expense of low achievers" (p. 320). Little research, however, exists that compares whole class, between-class, and within-class flexible grouping arrangements in terms of student achievement.

Concerns About Grouping Practices

Ability grouping practices have come under attack the past two decades because of concerns over issues of social and economic equity (Oakes, 1985; Slavin, 1990) and potential damage to students' self-concept and self-efficacy. However, Kulik and Kulik (1982) and Marsh and Parker (1985) found little evidence to substantiate these concerns, Schunk (1996) defined self-concept as "one's collective self-perceptions that are formed through experiences with, and interpretations of, the environment, and that are heavily influenced by reinforcements and evaluations by significant other persons" (p. 448). Bandura (1994) defined self-efficacy as "people's beliefs about their capabilities to produce designated levels of performance that exercise influence over events that affect their lives" (p. 71). Oakes (1985) and Slavin (1990) expressed concern that the self-concept and self-efficacy of students who are placed in low ability groups will suffer due to the stigma of such an assignment. However, Kulik and Kulik (1982) found in 15 controlled studies of between-class ability grouping and self-concept that the average effect size was -.06, a negligible effect. They suggested that effects of grouping on self-concept or self-esteem may be slightly positive for low ability students and slightly negative for high ability students. This effect on low ability students may be due to their opportunity to interact with the teacher and others in the classroom without the sometimes intimidating presence of high ability students. On the other hand, high ability students often suffer an early drop in self-concept or self-esteem due to the presence of other high ability students in their group (Marsh & Parker, 1985). This drop usually corrects itself within a brief period of time. Additionally, students of different ability levels may need different types of instruction to facilitate learning.

Feldhusen and Moon (1992) proposed that educators must be responsive to the reality that students begin new units of study with differing abilities, learning styles, and motivation levels. They continued, "some [students] are ready for fast-paced, high-level, very abstract instruction; for others instruction must be adjusted to fit their particular needs or deficiencies" (p. 64). Special grouping arrangements may be necessary to meet the ever-varying achievement levels of students in heterogeneous classrooms.

A Critique of Slavin and Oakes

The major sources of opposition to ability grouping have been Robert Slavin and Jeannie Oakes. Their research is quoted by both educators and researchers as the basis for abolishing or curtailing programs that may smack of ability or homogeneous grouping. But other researchers (Bode, 1996; Kulik, 1992; Rogers, 1993) have outlined flaws in their research.

First, Bode (1996) proposed that the controversy over ability grouping has become one of equity versus excellence. The opponents of ability grouping stress its inequitable effects, especially on those in the low groups. Bode suggests that research supporting the equity argument (Eder, 1981; Oakes, 1985; Page, 1965; Rosenbaum, 1980) is largely qualitative and anecdotal in nature. She also suggests "some of these contradictory conclusions can be attributed to the fact that different outcomes — academic versus social — are being referenced" (p. 1).

Second, in Slavin's "best-evidence synthesis" of research on comprehensive ability grouping at the elementary level, he purposely eliminates studies that include any special classes for low or high ability students (e.g., resource classes for special education or gifted students). He suggests that it would be unfair to compare these classes to those with mixed-ability students because there are typically curricular adjustments made in these special classes (Slavin, 1987).

A third flaw in the majority of the research on ability grouping is that most studies reviewed used aptitude or ability tests to regroup the students for instruction (Rogers, 1991). Most elementary schools today that use a form of ability grouping do not use IQ or aptitude tests as a placement tool. They are more likely to use specific achievement tests or demonstrated performance as a means to group students either between or within classes.

A fourth problem lies in Slavin's conclusions regarding ability grouping. He emphasizes one major review of ability-grouping studies published by Goldberg, Passow, and Justman (1966) in which IQ tests were used as the preassessment for initial placement, there was no evidence of any curricular adjustment, and the comparison of achievement gains among groups was nonsignificant. After reporting nonsignificant results in many of the studies he analyzes, he concludes that mixed-ability classrooms are more effective in raising student achievement levels.

A final problem with the majority of research on ability grouping is that it is approximately 25 years old. Typically, opponents of ability grouping have focused on studies of tracking or XYZ homogeneous grouping arrangements, which have fallen out of favor in most of the educational landscape. Additionally, with the exception of a few correlational studies of the Second International Mathematics Symposium (SIMS) and Third International Mathematics & Science Symposium (TIMSS) data (National Center for Education Statistics, 1999), there have been few controlled studies of the effects of different types of grouping arrangements on student achievement, especially those arrangements that include curricular adjustment.

Summary

Whole-group instruction is characterized by a single, set curriculum delivered at the same pace for all students. Between-class Joplin grouping involves the preassessment of specific skills and prior knowledge that necessitates assignment of students to a different teacher for instruction in that skill or content area. Within-class, or flexible small grouping, is characterized by preassessment and placement of students into small groups within their regular classroom setting. Researchers are divided on the effects of such grouping arrangements, but most agree that some form of temporary ability grouping, based on a specific aptitude in a skill or content, when complemented by appropriate instruction, may have significant effects on student achievement. Grouping practices alone will have only small to moderate effects on achievement if they are not complemented with appropriately modified and differentiated curricula (Kulik & Kulik, 1992; Rogers, 1993; Slavin, 1987).

Textbook-Based Curriculum

In his seminal studies, Goodlad (1966,1990), has criticized educational policymakers for failing to modify or improve classroom organization and instruction. He mused that if students from the early 1900s were magically transported to the classroom of the 1990s, they would recognize virtually every facet of the school day (1966). Even more critical, in this era of high-stakes standardized testing, one curriculum, geared to drill and practice prior to the test, dominates the modern classroom. According to Goodlad (1966), "too often, schools reward only that which is easily measured. And what is easily measured may be inconsequential in the conduct of human affairs" (p. 17).

Curriculum Revision or Modification

Cawelti (1999), Erickson (1998), Gardner (1999), Levin (1987), Wiggins and McTighe (1998), and Renzulli (1988,1994) have been instrumental in providing educators with strategies to modify, or remodel, existing units of study. Curriculum modification includes the analysis and removal of unchallenging and repetitive content; the enhancement of existing curricular units through the use of advance organizers, higher level questioning strategies, and critical thinking skills (Halpern, 1996; Paul, Binker, Jensen, & Kreklau, 1990); the connection of the unit of study to the disciplines (Bruner, 1975; Gardner, 1999; Phénix, 1958; Renzulli, 1988), and the design of units of study based on interdisciplinary concepts (Erickson, 1998; Jacobs, 1989; Kaplan, 1986).

Remodeled curriculum. Paul, Binker, Jensen, and Kreklau (1990) define curriculum "remodeling" as the process whereby teachers critique their lesson plans and formulate new ones based on that critical process. They suggest creating new lesson plans utilizing the major strategies of critical thinking. These 35 strategies are subdivided into three major categories: affective strategies that include thinking independently and developing confidence in one's reason; cognitive strategies: macroabilities that include transferring insights to new contexts and generating or assessing solutions; and cognitive strategies, microskills that include making plausible inferences or predictions and recognizing contradictions. The major guiding premise is that students will become autonomous, precise, and fair-minded thinkers. Using Paul, Binker, Jensen, and Kreklau's method, lesson plans are remodeled or enhanced to address higher order critical thinking processes.

Essential understandings. Erickson (1998) proposed a curriculum development plan that develops sophistication in knowledge, understanding, and the ability to perform. She suggested that this systems approach should address four critical components: (a) student outcomes — what students should know, understand, and be able to do based on the identified knowledge, skills, and abilities they will need for the 21st century; (b) the critical content, key concepts, and essential understandings that frame the knowledge base of different areas of study; (c) the major process and skill abilities that ensure quality performance; and (d) quality assessments for measuring standards-driven performance. She contends that teachers may begin to address these components if they acknowledge the essential understandings of a unit of study (i.e., the "big ideas" or key principles and generalizations) and allow those understandings to guide their curriculum development. According to Erickson, "essential understandings are the foundational ideas on which students build increasing conceptual depth and understanding" (p. 47). Teachers can facilitate students' essential understandings by constructing curricula that focus on the "big ideas" or key concepts and principles of a discipline, rather than a series of random, unconnected, and, usually, unlearned facts and skills.

The structure of the disciplines. Bruner (1960) suggested that if students could grasp the structure of a subject, they could relate other ideas to it meaningfully. The study of a field within the context of the disciplines includes the location of that subject within the history of knowledge, the methodologies employed by those who are the practicing professionals in the discipline, the major principles and concepts of the field, and the connections that field has with others in the history of knowledge. Brimer explained that students have limited exposure to the materials and content they are to learn. The key question becomes, "How can this exposure be made to count in their thinking for the rest of their lives?" He continued that understanding the structure of the subjects taught is the "minimum requirement for using knowledge for bringing it to bear on problems and events one encounters outside the classroom" (p. 59).

Goodlad (1966) also extolled the virtues of a curriculum that is developed with the structure of knowledge in mind.

The teaching and learning of structure, rather than simply the
mastery of facts and techniques, is at the center of the
classic problem of transfer. The school curriculum should be
planned to reveal continuing threads -ideas, generalizations,
principles, concepts, methods — by means of which
specific learnings might be related effectively to one another.
These threads are derived from at least three sources: the
developing characteristics of children, the subject matter
disciplines, and the nature of society, (pp. 11-16)

Gardner (1999) added that when an individual truly understands a concept, skill, theory, or domain of knowledge, she or he is capable of applying that knowledge appropriately in a new context. He scolded purveyors of the cultural literacy approach to learning (Hirsch, 1987), "with its promise of five minutes on every topic" (p. 118). He contended that without a disciplinary way of thinking, "cultural literacy lacks an epistemological home; it amounts to a hodgepodge of concepts and facts wanting to be used somehow, somewhere, sometime. Moreover, absent such disciplinary treatment and glue, the facts are likely to be soon forgotten" (p. 118). This problem becomes more acute in the global technological age in which teachers cannot possibly teach students all of the facts and skills that multiply exponentially on a daily basis.

The multiple menu model. Renzulli, Leppien, and Hays (2000) introduced a method of advanced curriculum development for teachers and curriculum developers in the upper elementary and secondary grades entitled the Multiple Menu Model. This model provides a guide for curriculum development that proceeds from several menus of curriculum techniques. These menus include a knowledge menu (i.e., the structure, definition, and location of the topic within the fields of knowledge, as well as the major concepts and principles of the field and the facts, conventions, and trends of the field of study). The instructional techniques menu includes a list of objectives and instructional strategies used in the study, a sequential list of the actual teaching and learning activities, and a section that allows for the "artistic modification" based on teacher talents, interests, and particular knowledge. Finally, the guide includes an instructional products menu, which allows students to create new knowledge and information and to demonstrate that knowledge in the form of abstract ideals (e.g., values, appreciations, and cognitive structures) and concrete products (e.g., written, spoken, or artistic) that should be presented to an authentic audience. In utilizing this model for curriculum development, teachers and developers are able to combine the most important aspects of each unit with the effective enrichment techniques of authentic learning; (i.e., authentic resources, products, and audiences).

The parallel curriculum model. Tomlinson, Kaplan, Renzulli, Purcell, Leppien, and Burns (2002) updated the literature on curriculum revision by developing the Parallel Curriculum Model, a model for developing engaging and challenging curriculum for average and gifted learners. The Parallel Curriculum Model consists of four parallels, or categories of learning experiences. According to the authors, the Core curriculum is a plan that includes a set of guidelines and procedures to help educators address the core concepts, principles, and skills of a discipline. The Core curriculum specifies those key concepts, principles, and representative topics that form the core of student learning. Unlike the laundry-list style of cultural literacy, the Core curriculum suggests those ideas and concepts that aid essential student understanding of a field of study. The Connections curriculum is a set of guidelines and procedures to help educators connect overarching concepts, principles, and skills within and across disciplines, time, cultures, places, and/or events. The Practice curriculum helps students understand, generalize, and transfer essential knowledge in a field to authentic, discipline-based problems. The Identity curriculum helps educators connect the disciplines to students' own lives, personal growth, and future development. The Parallel Curriculum Model is a powerful blend of gifted education theories, models, and strategies proposed by Renzulli (1988), Kaplan (1986), and Tomlinson (1995,1999).

Curriculum Differentiation

Introduction. Bechtol and Sorenson (1993), Kaplan (1986), Passow (1962), Renzulli (1994), Tomlinson (1995,1999), VanTassel-Baska (1994), VanTassel-Baska and Little (2003), and Wang and Walberg (1985) have proposed models for curriculum differentiation that include the extensive use of pre-assessment to determine students' strengths and interests; flexible grouping practices based on those pre-assessed areas; and the differentiation of existing curricula, which suggests increasing the breadth (interest, choices, and learning style variation) and depth (lessons for different ability levels) of the curriculum. Passow defined differentiated curriculum as "that which embodies the recognition of differing learning rates, styles, interests, and abilities" (p. 6), while Ward (1980) explained the need to provide appropriate instruction at students' ability levels. The goal of curriculum differentiation is to elicit learner responses commensurate with their gifts or talents.

Principles of differentiated curriculum. Tomlinson (1999) suggested four principles that should guide educators as they create a differentiated classroom: (a) teachers focus on the essential concepts, principles, and skills of each subject; (b) teachers attend to student differences, which are guided by their experiences, culture, gender, genetic code, and neurological wiring; (c) teachers realize that assessment and instruction are inseparable; and (d) teachers modify content, process, and products to meet individual students' levels of prior knowledge, and learning, thinking, and expression styles. In a differentiated classroom, teachers are attuned to student differences and attempt to align their curricula to address those differences.

VanTassel-Baska (1986,1994) summarized the major methods of curriculum differentiation with four adjustments that teachers should consider for students with different levels of readiness or prior knowledge: deleting or compressing the basic curriculum that the students have mastered, or could master, with little instruction; concentrating on higher level thinking skills (Feldhusen, 1989) and the methodology of the practicing professional (Renzulli, 1977); providing depth to the curriculum by concentrating on the interrelationships among bodies of knowledge or the structure of the disciplines (Bruner, 1960; Kaplan, 1986; Phenix, 1964; Renzulli, 1988); and encouraging self-directed learning so that students can become independent inquirers.

Wang and Walberg (1985) summarized the basic premises underlying curriculum differentiation: individuals learn in different ways and at different rates; it is the major responsibility of schools to accommodate these differences to maximize each student's education. Rather than assuming that all students can and do learn in the same way and at the same rate, it is imperative for educators to acknowledge those differences, assess them, and create curricula that address those differences. In accepting that students demonstrate many individual differences, researchers must be prepared to isolate and study those effects that may exist within schools rather than between them.

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By Carol L. Tieso

She completed her Ph.D. at the University of Connecticut in June, 2000. Her research interests include the impact of flexible grouping and curriculum differentiation models on students' achievement and addressing the social and emotional needs of gifted, talented, and creative students.