skip to main navigation skip to demographic navigationskip to welcome messageskip to quicklinksskip to features
  • Continue Your Membership
  • WEAC Member Benefits

Educational Issues Series: Class Sizes



Helen Pate-Bain (1992), in her report on the Tennessee STAR class size study, concluded, “We view education not as a mass- production effort, but as a personal and individual experience. The model is not the factory. The focus is on serving clients. Class-size research is not an attempt to reduce class size; at its best it is an effort to find appropriate casework loads, because much of sound educational practice consists of individual instruction, coaching, mentoring, and tutoring (p. 256)."

We’ve learned much recently about instructional practices and how students learn. Yet, the controversial issue of class size and its effect on educational practices and student outcomes continues to be confusing and often contradictory.

Effective schools research has extended its research agenda by focusing on an expanded number of variables that are presumed to be related to student achievement. Schools are now perceived as a cultural entity where the complex interplay of multiple variables affect the lives of all who learn and teach in those institutions. As the metaphor for American schools has shifted from an assembly line to that of a caring, learning community, the class size research agenda has also shifted to include such variables as instructional method, teacher morale and stress, teacher work load, student behavior and attitudes, content areas, student characteristics, and grade level. Bennett (1987), in a review of more recent research, found broad agreement among researchers on the following general conclusions:

  • Smaller classes result in increased student-teacher contact.
  • Reductions in class size to less than 20 students without changes in instructional methods cannot guarantee improved academic achievement.
  • No single class size is optimal for all grade levels and subjects.
  • Smaller classes appear to result in greater achievement gains for students with lower academic ability and for those who are economically or socially disadvantaged.
  • Classroom management improves in smaller classes (fewer discipline problems).
  • Smaller classes result in higher teacher morale and reduced stress.
  • Individualization is more likely to occur in smaller classes.
  • Class size reductions alone do not necessarily lead to adoption of dramatically different instructional methods.
  • Class size appears to have more influence on student attitudes, attention, interest, and motivation than on academic achievement.
  • Smaller classes are beneficial for children at the primary level, particularly in math and reading.
  • Very small classes of five or fewer students produce considerably higher achievement (Bennett, p. 3).

As class size comes to be understood as only one variable in the complex culture of school life and as research methodologies appropriate to study this level of complexity are perfected, it will be possible to move beyond the search for the “correct” number of students to be assigned to any particular classroom.

Defining Class Size

Defining class size is tricky business. For example, a district may calculate the student-teacher ratio by including all licensed professional personnel and emerge with a ratio of 15.6 students per teacher. If all administrative and support personnel are omitted, the ratio may become 20 or more students per teacher. Neither ratio may reveal with much accuracy the conditions under which the average student is taught and learns in that district. The differences that occur among grade levels and subject areas are obscured in most class size statistics.

Allen (1992), in a Wisconsin class size study, found that the median number of students evaluated by elementary teachers was 25 while the mean number of students evaluated was 88. The larger mean number reflects the significant number of teachers of art, music and physical education who meet with hundreds of different students each school year.

In the same study, Allen found that the median number of students evaluated each year by middle, junior, or senior high teachers was 136 while the mean was 164. Over one quarter of the upper level teachers reported evaluating 200 or more students and 2.7% of those teachers evaluated 400 or more students each year! These data indicate that both mean and median numbers can be misleading if there are significant numbers of teachers who meet with very large or very small numbers of students each day.

As generic class size research has diminished in popularity, other related issues have received more attention. Teacher load, defined as the total number of students taught each day, has emerged as an indicator of school adequacy (Bennett, 1987). Teacher load has become a key variable in schools where the quality and duration of student-teacher interaction is valued.

Although numbers of students instructed each day or evaluated each year are illuminating, such numbers do not reflect the total range of responsibilities confronting the classroom teacher. Research on teacher stress and morale has begun to examine teacher workload as a meaningful indicator of quality (Bennett, 1987). The number of classes, the number of preparations, subjects taught outside of one’s specialty, student diversity, non-teaching responsibilities (such as supervision of extracurricular activities) and school facilities, inservice obligations, and other professional responsiblities are included in workload research. The workload issue becomes more complex when specific teaching responsibilities are considered, as in the case of a secondary English teacher responsible for 150 composition students.

The understanding that schools are complex cultural entities and that school quality is dependent on the quality of student-teacher interaction has produced a new generation of class size research which explores relationships among a wide range of variables. That research is reviewed below.

The Research Base

The emergence of increasingly sophisticated research methodologies has resulted in the reexamination of existing studies and has produced a number of new research reports on the impact of class size on a wide range of variables. In 1986, the NEA published a review of major class size research reports. Several of these reports were of original class size research projects while others presented the results of the application of new analytical techniques to existing data (CLASS SIZE, 1986). For example, Glass and Smith (1978), reread, coded, and analyzed 77 empirical research studies that incorporated achievement test data on over 900,000 students. That meta-analysis yielded what Glass and Smith called “general trends” in the effect of class size on achievement.

The NEA report (CLASS SIZE, 1986, p.11), concludes: “The central theme which runs through the current research literature is that academic achievement does not necessarily improve with the reduction of student-teacher ratios unless appropriate learning styles and effective teaching styles are utilized. It is also evident that no single class size is best for all grade levels and all subject areas.”

The central themes which emerged from the NEA study were:

  • Smaller class size seems to result in higher achievement among students who are economically disadvantaged.
  • Students with lower academic ability seem to do better in smaller classes than in larger ones.
  • It may be that class size affects student attitudes more significantly than it affects achievement.
  • A direct effect of large class size is to lower the morale and increase the stress of teachers.
  • There is typically little to be gained from reductions in class size that do not bring class size below 30.

The most recent comprehensive review of existing research was completed by Robinson (1990), and used a cluster analysis approach. Studies were “clustered” into categories considered important for class size decisions such as grade levels, subject areas, student characteristics, student achievement, student behavior, and teaching practices. The results of part of Robinson’s analysis appear below.

Student Achievement

The most promising effects of small classes on pupil learning occurred in grades K-3 in reading and mathematics, particularly in classes of 22 or fewer students (Robinson, p.82). Two recent studies found that these gains could not be sustained in subsequent years without reinforcement.

In grades 4-8 the cluster of 21 studies indicated that smaller classes had a slight positive effect on student achievement, but not as great as in grades K-3. The gains were evident in reading and mathematics but not in other subject areas. The data for grades 9-12 did not indicate that smaller classes had a positive effect on student achievement; however, the number of studies done at the secondary level were few and even "small" classes ranged from as few as five to as many as 40 students. Economically disadvantaged and minority students performed better academically in smaller classes at all grade levels (Robinson, pp. 84-86).

Student Behavior and Attitudes

Studies in the K-3 cluster showed the most favorable relationship was between smaller classes and positive student attitudes and behavior. A minority of studies at other grade levels found positive results as well.

Teaching Practices

Although a minority of the studies reviewed reported more favorable teaching practices in smaller classes, there is no evidence that the opportunities presented by smaller class size are routinely exploited by teachers.

For example, in a two-year Toronto study, a substantial majority of teachers reported that they had given more individual attention to students and had made changes in classroom management, pupil evaluation, and classroom layout when working with smaller classes. However, these self-reported changes were not found in classroom observations by the researchers. In a 1987 New York City study that reduced class size from 26 to 16 pupils, researchers concluded, “Although it was expected that the reduced-class size would permit teachers to provide more small group and individualized instruction in all curriculum areas, no meaningful differences were observed . . . . (Robinson, p. 87).”


Robinson offers the following observations as a result of his cluster analysis:

  • The most positive effects of small classes on pupil learning occur in grades K-3 in reading and mathematics.
  • Studies examining student attitudes and behavior found the most favorable effects of smaller classes in the primary grades.
  • Smaller classes can positively affect the academic achievement of economically disadvantaged and ethnic minority students.
  • Within the midrange of 23 to 30 pupils, class size has little impact on the academic achievement of most pupils in most subjects above the primary grades.
  • The positive effects of class size on student achievement decrease as grade levels increase; however, the available studies in specific subject areas in the upper grades are limited in both number and quality.
  • Little, if any, increase in pupil achievement can be expected from reducing class size if teachers continue to use the same instructional methods and procedures in the smaller classes that they have used in larger classes (Robinson, p. 82).

Recent Research Data

Several recent studies of outstanding quality have emerged to strengthen the data base on class size and effective instruction. They include the Prime Time project in Indiana, Project STAR in Tennessee, and the WEAC Class Size and Teaching Assignment study in Wisconsin. These studies are described in some detail below.

Prime Time

In 1984, the state of Indiana allocated money to reduce first grade classes to 18 students; in 1985, money was budgeted to reduce second grade classes to 22 students; and in 1986, money was budgeted for a reduction in either third grade classes or kindergarten classes. Districts were reimbursed for their efforts to reduce class size on the basis of average enrollments. Funds were prorated for districts with classes averaging more than the targeted numbers; thus, classes were smaller than targeted in some districts and much larger in others (Mueller, Chase, and Walden, 1988). As an alternative to reducing class size, districts were permitted to hire teacher aides; each aid counted as .33 FTE (full time equivalent) in the student-teacher ratio.

The achievement effects of this class size project were mixed. Project analysis, done by Indiana University faculty, found that student achievement, as measured by traditional standardized tests (Iowa Test of Basic Skills and Stanford Achievement), showed strong gains in first grade reading levels with smaller gains in mathematics. Second grade gains were much more limited. Robinson’s (1990) analysis of the Prime Time project concluded that while there were small but positive gains during the first year of the project, extending the effort to third grade classes did not have any significant effect on either reading or mathematics test scores.

Prime Time teachers who were interviewed believed that the project had a variety of positive benefits. They indicated that students received more individual attention, that students received more immediate feedback, that both below-average and above-average students achieved more, that a greater variety of instructional materials were used, that the instructional atmosphere was less hectic, that teachers assigned more homework, and that teachers were happier and more enthusiastic about their teaching (Mueller, Chase and Walden, p.50).

Project STAR

Tennessee’s four-year study of class size effect has, to date, produced the most compelling data on class size, effective teaching strategies, and the sustainability of early student achievement gains that is currently available. Project STAR, a longitudinal study, followed students from kindergarten in 1985-86 through the third grade in 1988-89. A selected number of fourth grade students (4,230 students in 216 classes) were part of a Lasting Benefits Study done in 1989-90.

Project STAR analyzed student achievement and development in three types of classes: small classes (13-17 students per teacher), regular classes (22-25 students per teacher), and regular classes (22-25 students) with a teacher and a full-time teacher aide (Word, et al., 1990). The project included 17 inner-city, 16 suburban, 8 urban, and 39 rural schools in order to assess the effects of class size in different school locations. A major strength of the study was the “within-school” design which required each school to have at least 57 students at the appropriate grade level so that each school would contain at least one of each class type (small, regular, and regular/aide). Students (6,000) and teachers were randomly assigned to class types.

Achievement Results

Student achievement was measured with three instruments: the Stanford Achievement Test, STAR’s Basic Skills First Criterion Tests, and Tennessee’s Basic Skills Criterion Tests. Kindergarten results showed a definite advantage for small classes but no significant advantage for the regular/aide classes. By the end of the first grade, Project STAR students in small classes were outperforming students in regular and in regular/aide classes by substantial margins (statistically and educationally significant).

The presence of a teacher aide in a regular class benefited students but not as much as the small class condition. Students in second grade small classes continued to outperform students in regular and regular/aide classes on all tests. Differences between students in regular and regular/aide classes were not significant. By grade three, the pattern of results established in kindergarten had become firmly fixed. A strong class-size effect was evident in all school locations (urban, rural, inner-city, and suburban) and for all students. The absence of a statistically significant teacher aide effect was consistent (Word, et al., pp. 10-13).

Several other findings were relevant:

  • The only consistent positive effect in regular classes with a full-time aide occurred in first grade.
  • Teachers reported that they preferred small classes in order to identify student needs and to provide more individual attention, as well as to cover more materials.
  • The importance of the economic background of students was underscored by the finding that, in every situation, those students who were not economically eligible for the free lunch program always outperformed those students who were in the free lunch program (Pate-Bain, et al., p.254).

The achievement benefits of small class size were cumulative. The top achieving STAR classes in the study were categorized by class type each year.That is, in the first year 55% of the "top classes" were small classes (13-17 students). By the time these students reached third grade, 78% of the "top classes" consisted of small classes. In other words, over time, the benefits of small class size on student achievement became increasingly apparent.

A Lasting Benefits Study was conducted with a sample of fourth grade students in 1989-90. The LBS study yielded clear and consistent results:

“Students who had previously been in small STAR classes demonstrated significant advantages on every achievement measure over students who had attended regular classes. Further, these results favoring small classes were found to be consistent across all school locations'' (Pate-Bain, et al., pp. 254-255).

Other Results

Teacher aides were less effective than small classes in enhancing student performance at each grade level. Although aides performed a variety of clerical, custodial, and instructional tasks, the pattern of aide activities was not related to student achievement. While teachers liked teacher aides, the teacher aide did not have much effect on student learning in Project STAR.

If educators are to make the best use of opportunities provided by small class size, they must be aware of what constitutes effective teaching in such settings. STAR researchers studied the classroom strategies used by the 49 first grade teachers whose small classes had made the greatest gains in achievement. These effective teachers displayed similar affective behaviors and characteristics:

Their enthusiasm was obvious as they engaged in “acting,” demonstrating, and role-playing activities. The teachers frequently expressed positive attitudes toward children, emphasized positive behavior, praised success, and used humor to promote learning and to motivate students. A love of children seemed to permeate their professional repertoires. The most effective teachers engaged their students through the use of creative writing, hands-on experiences, learning centers, and math manipulatives'' (Pate-Bain, et al., p. 255).

Project STAR recognized at the outset that small class size does not make a difference if teachers do not change the way they teach. A subgroup of randomly selected STAR teachers were selected for three days of inservice training before the project began. The training was designed to help them teach more effectively in whatever class type they were assigned to teach. Subsequent data revealed that there were no significant differences in student achievement in reading or mathematics between classes where the teachers were trained and all other classes where the teachers had not been trained. Several findings emerged:

  • Teachers with small classes must not only be trained to be effective in such settings, but they must also be committed to try new skills and procedures.
  • Effective inservice training must include time to visit other teachers who have had success in working with small classes.
  • Inservice work must include training in effective communication with the home, in involving the family with the education of their children, and in making home visits as part of regular instructional responsibilities.

Project STAR has set high standards for future class size research and has provided clear guidelines for schools committed to improving student achievement in grades K-3.

Class Assignment and Teaching Assignments Study (WEAC)

This WEAC study (Allen, 1992) extended the parameters of traditional class size research by examining teacher load and workload, the allocation of the teacher workday, the impact of special needs students on classroom instruction, and the consequences of classroom conditions for teacher stress and morale. Allen surveyed a random sample of 1,150 elementary and 1,500 middle, junior and senior high teachers in Wisconsin in order to ascertain the qualitative conditions of classroom life. Student achievement data was not reviewed.

The Wisconsin study revealed that there was little difference in the length of the school day reported by teachers at the various grade levels; the median length of the school day was 467 minutes for elementary teachers and 468 minutes for teachers in the upper grades. However, some variation was reported in “direct contact” time, with elementary teachers reporting 325 minutes each day in direct contact with students and teachers at the middle, junior and senior high grades reporting 283 minutes of direct contact time (Allen, p. 8). These data do not include supervisory time.

The complexity of teacher workload was addressed in a number of ways in this research. It was determined that for teachers meeting with the same group of students each day (60% of elementary teachers and 4% of middle, junior and senior high school teachers) the median number of students in class was 24. However, evaluation responsibilities were determined by Allen to be a more accurate indicator of workload. These data revealed that the median number of students evaluated by elementary teachers each year was 25 while the mean number was 88. The median number of students evaluated each year by middle, junior and senior high school teachers was 136, while the mean was 164. Over one quarter of these teachers reported evaluating 200 or more students each year (Allen, pp. 10-11). As noted earlier, teachers of art, music, and physical education confront heavy workload and evaluation responsibilities.

The impact of student diversity, specifically the numbers of students with Exceptional Educational Needs, was also addressed. The number of students identified as having special needs in Wisconsin schools has increased from 5% to more than 9% of the student population over the past fifteen years. These students require extra attention and more preparation time if they are to be successful in the classroom. The WEAC study found that the median number of EEN students taught by elementary teachers was between 4 and 5 while the median number taught by teachers at the upper grade levels was nearly 8. To assess the impact of these numbers on classroom instruction, Allen created an "EEN Index Number." The number reflects the total number of minutes of instructional time during which the teacher is in contact with EEN students. It is a measure of the increased responsibility the teacher confronts in such circumstances. The index number is calculated by multiplying the number of EEN students present by the number of minutes the teacher meets with each student on a daily basis. For example, if Teacher A meets with three EEN students for ten minutes each day and Teacher B meets with three EEN students during the entire school day (assume 325 minutes), the Index Numbers would be 30 and 975 minutes, respectively.

Elementary teachers reported a median index number of 600 minutes spent each day with students who have special needs, while teachers at the middle, junior and senior high reported an index number of 400 minutes per day (Allen, pp. 13-14). The amount of total contact time, as an indicator of professional responsibility, is more important than is the total number of EEN students enrolled.

Between two-thirds and three-fourths of the teachers responding to the WEAC study indicated that they would make changes in how they teach if they had significantly fewer students in their classes.

Changes mentioned included:

  • more individual attention
  • more written assignments
  • more creative activities
  • more opportunity to monitor the progress of each student
  • more problem-solving activities, more projects, more essay tests
  • more attention to gifted children, and
  • more field trips (Allen, p. 17).

Between 8 and 14% of the teachers indicated they would not make changes in how they would teach and about 18% were not certain.

Implications of the WEAC Study

In a previous study of teacher mobility in Wisconsin, Allen and Helming (1991) found that a significant number of teachers expressed high levels of job dissatisfaction. Thirty-one percent of Wisconsin teachers had given “quite a lot” or “a great deal” of thought to changing teaching jobs, leaving teaching, or both. Large class sizes and excessive responsibilities contribute to high stress levels and high levels of job dissatisfaction among teachers. This research offers new insights into the complexities of teacher workload and , by implication, suggests avenues by which student achievement may be enhanced.

Summary and Recommendations

Major findings presented in the research on class size include:

  • There is probably no optimum class size for all types of students, in all subject areas, and at all grade levels.
  • Smaller classes produce the necessary, though not sufficient, conditions for successful teaching and learning.
  • Reduced class sizes in grades K-3, in the range of 13-17 students per class, significantly enhance student achievement.
  • Reductions in class sizes to less than 20 students without changes in instructional methods cannot guarantee enhanced student achievement.
  • Small class size, in the range of 13-17 students, benefits all students in all contexts at the K-3 level.
  • Regular-size classes with a teacher aide are less effective than small classes in enhancing student achievement at the K-3 level.
  • There are identifiable teaching behaviors which will enhance the benefits of a small class design; these include individual instruction, coaching, mentoring, and tutoring.
  • The evidence favoring small class size at the upper grade levels is weak because teaching behaviors appear to be more rigid and research methodologies have been inadequate.
  • Teacher inservice opportunities must accompany reduced class sizes so that appropriate teaching can be developed and reinforced.
  • Class size definitions vary, depending on whether mean or median numbers are used.
  • Class size averages may obscure the fact that some students, such as EEN, require extra attention and care.
  • Both class size and teacher workload (the number of students evaluated during the year) are important indicators of school quality.

This review of existing research, with all of its incumbent limitations, suggests that increasing student learning by reducing class size is a complex matter. It suggests that class size reductions should be targeted to specific student groups for specific purposes, that teachers must receive the training needed to make the most of the new learning opportunities available in smaller classes, and that little is known about how to effectively approach the problem of large student numbers in the upper grade levels without confronting the basic structures of those institutions.


Allen, Russ. CLASS SIZE AND TEACHING ASSIGNMENTS OF WEAC’S TEACHER MEMBERS. Madison, Wisconsin: Wisconsin Education Association Council, 1992.

Allen Russ and Helming, Margaret. TEACHER MOBILITY IN WISCONSIN. Madison, Wisconsin: Wisconsin Education Association Council, 1991.

Bennett, Susan. NEW DIMENSIONS IN RESEARCH ON CLASS SIZE AND ACADEMIC ACHIEVEMENT. Madison, Wisconsin: University of Wisconsin, Madison, 1987.

Cotton, Kathleen. SUMMARY OF RESEARCH ON CLASS SIZE. Portland, Oregon: Northwest Regional Educational Laboratory, 1988.

Glass, Gene V. and Smith, Mary L. META-ANALYSIS OF RESEARCH ON THE RELATIONSHIP OF CLASS SIZE AND ACHIEVEMENT. San Francisco: Far West Laboratory for Educational Research and Development, 1978.

Hawley, Willis D. et al., “Good Schools: What Research Says About Improving Student Achievement.” PEABODY JOURNAL OF EDUCATION (Summer 1984).

Mueller, Daniel J.; Chase, Clinton I.; and Walden, James D. “Effects of Reduced Class Size in Primary Classes.” EDUCATIONAL LEADERSHIP (February 1988): 48-50.

Pate-Bain, Helen; Achilles, C.M.; Boyd-Zaharas, Jayne; and McKenna, Bernard. “Class Size Does Make a Difference.” EDUCATIONAL LEADERSHIP (November 1992): 253-256.

Robinson, Glen E. “Synthesis of Research on the Effects of Class Size.” EDUCATIONAL LEADERSHIP (April 1990): 80-90.

WHAT RESEARCH SAYS ABOUT CLASS SIZE. Washington, D.C.: National Education Association, February, 1986.

Word, Elizabeth, et al., STUDENT/TEACHER ACHIEVEMENT RATIO (Star): TENNESSEE’S K-3 CLASS SIZE STUDY. Nashville, Tennessee: Tennessee State Department of Education, 1990.

This document was prepared by Ken Kickbusch of the WEAC Professional Development Division

Posted May 30, 1996