Achievement Effects of Ability Grouping in Secondary Schools: A Best-Evidence Synthesis

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NICHCY’s Structured Abstract 73 describes the following:

Title | Achievement Effects of Ability Grouping in Secondary Schools: A Best-Evidence Synthesis

Author | Slavin, R.E.

Source Review of Educational Research, 60(3), 471-499

Year Published | 1990

A “best evidence” review synthesis, which incorporates features of meta-analytic and traditional literature reviews, is used in this review of studies on the effects of ability grouping on secondary school students’ achievement. The focus was on 29 studies that compared between-class ability grouping to heterogeneous placements. Effect sizes were used to characterize study results. Findings indicate that comprehensive between-class ability grouping plans, different forms of ability grouping, and ability grouping by subject (except in social studies) had no effect on student achievement. The finding of zero effects of grouping for all ability levels contradicts earlier conclusions that demonstrated benefits of ability grouping for high-level students and detriments for low-level students. Explanations for this discrepancy are discussed. An implication is that policy decisions about ability grouping must be based on criteria other than effect on academic achievement. A recommendation is made for reduction of between class ability grouping practices and consideration of cooperative learning methods. An extensive bibliography and statistical tables are included. (LMI)

Ability grouping of students has a substantial history of use in elementary and secondary schools. There are two mostly commonly used types of ability grouping: between-class and within-class ability grouping.

  • Between-class ability grouping is a school-level practice; it refers to forming classrooms so that students of similar ability are placed together.
  • Within-class grouping is a teacher-level practice, in that the teacher groups students of similar ability together within a single class.

There has been an ongoing debate in education about whether or not either type of ability grouping helps or harms student achievement.

The argument in favor of ability grouping is that it allows teachers to challenge high achievers, while providing remediation, repetition, and review for low achievers.  Those in favor of ability grouping claim that, in mixed-ability classrooms, teachers must teach to the average level, which is likely to bore the high achievers at the same time it is too fast-paced for the lower achievers, thereby creating an ineffective educational environment for most of the children in the class.

The arguments against ability grouping usually focus on its two-fold negative impact on low achievers. When separated from high-achieving peers, low achievers not only lose the positive example of their peers but also now work under the lowered expectations from their teachers. In addition, some researchers believe that low-achieving groups are likely to receive lower quality instruction than high-achieving groups, further increasing the achievement gap. This meta-analysis examines not only whether ability grouping is effective, but also whether secondary school students benefit more or less from ability grouping depending on the academic subject it is used in or the type of ability grouping plan being implemented.

Research Questions
What are the effects of ability grouping practices on the achievement of secondary school students?

Research Design

  • Number of Studies Included | 29
  • Number of Subjects | Not reported
  • Years Spanned | 1927-1986

Research Subjects
Secondary school students in classrooms divided into ability groups.

Age/Grade of Subjects
7th through 12th grade

Specified Disability
Specific disabilities were not reported, but many ability groups were split by high, average, or low IQ/achievement.

Students were grouped by ability in different subjects (e.g., social studies, mathematics, science, literature, etc).

Duration of Intervention
The studies varied in length between 1 semester and 5 years.


  1. Ability grouping had little or no beneficial effect on the achievement of secondary students on standardized tests.
  2. There was much more evidence showing the ineffectiveness of ability grouping in Grades 7-9, but the more limited evidence that did exist from Grades 10-12 also showed ability grouping to be ineffective.

Combined Effects Size

  1. “Across the 29 studies the effects of ability grouping on student achievement are essentially zero.
  2. The median effect size for the 20 studies from which effect sizes could be estimated was -0.02, and none of the 9 additional studies found statistically significant effects” (p. 484).

In contrast to a similar meta-analysis (also by Slavin) on the effect of ability grouping in elementary schools, in which it was found that certain grouping practices were successful, this review of ability grouping in secondary schools found that ability grouping plans have little or no beneficial effect on the achievement of secondary students on standardized tests.

These findings differ from those studies comparing the achievement of students in different tracks, which generally found ability grouping had positive effects for high achievers and negative effects for low achievers. Slavin explains that one reason for this is that the impact of tracking often has to do with the way it effects students’ course selection both in terms of the number of courses they take in different subjects and the rigor of those courses. These studies only compared the effect of ability grouping on students who were taking different levels of the same course, such as a geometry class filled with high achievers versus a geometry class of low achievers. It did not examine the differential effects of tracking on course selection or number of courses taken, such as a student in a low track only taking functional math classes and a student in a high track completing all the mathematics courses offered up through calculus.

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