Abstract
The study examined effects of homogeneous and heterogeneous achievement grouping on mathematics learning through concept and skill games. Subjects were 164 seventh graders; half played probability concept games, and half played a fractions skill game. On the basis of scores on pretests related to game content, groups of three or four classmates of similar or different achievement were formed. These groups played the games twenty minutes, twice weekly, for four weeks. For each game-by-achievement grouping combination, posttest scores were higher than pretest scores (p < .01); there were no treatment, sex, or interaction effects. Assignment based on prior achievement to game-playing groups need not be a critical concern either for classroom or research use of games.