A meta-analysis of findings from 31 separate studies showed that ability grouping has significant positive effects on the academic performance of elementary school children. The benefits of grouping tended to be small in the typical study of achievement --an increase from the 50th to the 58th percentile for the typical student in a grouped class. One subgroup of studies, however, produced especially clear effects. In this type of study, students of high ability, or "gifted" students, were put into special classes in which they received enriched instruction. Studies of this type usually reported significant results and usually reported effects on achievement that were moderate in size. Meta-analysis also showed that ability grouping had trivially small effects on the self-concepts of elementary school pupils. (Author/RH)