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

This article reviews research on the effects of ability grouping on the achievement of secondary students. Six randomized experiments, 9 matched experiments, and 14 correlational studies compared ability grouping to heterogeneous plans over periods of from one semester to 5 years. Overall achievement effects were found to be essentially zero at all grade levels, although there is much more evidence regarding Grades 7–9 than 10–12. Results were similar for all subjects except social studies, for which there was a trend favoring heterogeneous placement. Results were close to zero for students of all levels of prior performance. This finding contrasts with those of studies comparing the achievement of students in different tracks, which generally find positive effects of ability grouping for high achievers and negative effects for low achievers, and these contrasting findings are reconciled.