Multiage/multiability grouping is when more than one grade level of students is grouped in a classroom. This report summarizes the research on multiage/multiability grouping in the primary grades. The paper, which is intended for use in Kentucky's educational system, focuses on quantitatively based comparative research syntheses. The text describes the Primary Program and looks at factors that may explain improved learning and test results. It asks numerous questions: "What are the problems in implementing the multi-age/multi-grade grouping attribute of the Primary Program?""Does the multi-age requirement limit implementation of other critical attributes of the Primary Program?""Are there inconsistencies between the Primary Program and other components of the Kentucky Education Reform Act?""What are the findings from research studies on multiage/multigrade grouping?" and "What effect has Kentucky's Primary Program had on the number of children labeled 'exceptional' in grade 4?" Each question is followed by a summary of research addressing that question. The findings indicate that learning is enhanced not by how schools group students for instruction, but by what they do within those groups. (RJM)