The Effects of Ability Grouping in Secondary Schools: A Response to Slavin’s Best-Evidence Synthesis

Abstract

The motivation for this response to Slavin's meta-analysis of ability grouping in secondary schools is the concern that social scientists, and especially educational practitioners, might accept without further qualification the conclusions Slavin reaches and proceed to make decisions regarding practice and policy based on these conclusions. This outcome, I feel, would be inappropriate and perhaps misguided, for reasons to be outlined here. The time is ripe for a review of research on the effects of ability grouping. Recently, new conceptualizations of the organization of schools have been formulated, renewed interest in the instructional process has occurred, empirical research on ability grouping has burgeoned, and more and more of this research is being disseminated to the educational community. It is time to take stock in order to facilitate the difficult process of applying social science research on ability grouping to educational practice in schools. Slavin's review on ability grouping in secondary schools (middle, junior high, and high schools) parallels his recent meta-analysis of research on ability grouping in elementary schools (Slavin, 1987). In both reviews, the final conclusion Slavin reaches is predictable. Based on what he judges to be the best of the available research on ability grouping, he concludes that ability grouping has no direct effect on student achievement in English, Reading, or Mathematics. Ability grouping provides no advantage or disadvantage, compared to heterogeneous grouping, for student learning. The fact that the studies Slavin examines show no direct effect of ability grouping on student achievement is not surprising. The studies compare mean achievement scores of classes that are ability grouped to those that are not. Since means are averages, they reveal nothing about the distribution of scores in the two kinds of classes. Ability grouping may increase the spread of test scores while leaving the mean unchanged. This would occur if the practice had a differential impact on students with different abilities. Since teachers generally gear instruction to the ability level of the students being taught, students in a high ability group are likely to receive more and faster instruction and those in low ability groups less and slower instruction than pupils in an ungrouped class where instruction is geared to the average of the class. If greater gains of high achievers balance lesser gains of slow students in a grouped class, there should be no overall impact on the mean achievement of the class, compared to a heterogeneous class, even though the variance of the test scores in the two classes may differ markedly. Studies comparing only mean would show no direct effect of grouping on achievement.