The purpose of this study was to examine the effects of heterogeneous and homogeneous grouping on the mathematical achievement of students in third grade. Participants were 16 third graders in a self-contained classroom, assigned to either small homogeneous or heterogeneous group for math instruction for 7 weeks. Pretest-posttest scores and growth of students in both groups were statistically analyzed to determine effect on student achievement. Results indicate that there was no statistically significant difference in effect on student math performance between the heterogeneous and homogeneous grouping types. Both grouping types resulted in comparable academic gains for students. There was not a significant difference between the two groups. Classroom implications are discussed.