SYSTEMS OF ABILITY GROUPING AND THE STRATIFICATION OF ACHIEVEMENT IN ELEMENTARY SCHOOLS.

This paper analyzes the effects of ability group systems on student achievement using data on fourth grade students in a single urban school district. Discussion focuses on two proposed explanations for the emergence of achievement differentials in grouping systems: The differential peers hypothesis and the differential instruction hypothesis. In the data analysis, processes of peer allocation and differential instruction were explored in the context of two types of instructional grouping systems: within-classroom grouping for reading instruction and across-classroom ability grouping. Both types of grouping arrangements had direct effects on reading achievement, demonstrating that-grouping systems reinforce initial inequalities in achievement. However, the two forms of grouping had different effects on processes of peer allocation and differential instruction. Instructional processes and peer group formation tended to disadvantage students in lower strata of the cross-classroom ability group system but to work in favor of students in lower strata of the within-classroom reading group system. The implications of these findings for a general theory of instructional grouping are discussed. [ABSTRACT FROM AUTHOR]