To maximize the benefits of cooperative learning groups, the students within each group should be heterogeneous in ability and personal characteristics” (Artzt and Newman 1990, 449). “Although groups can be formed by random assignment, heterogeneous grouping ensures a mixture of mathematical achievement, gender, and race/ethnicity. An occasional use of sociometric choice by students is possible, but homogeneous grouping is usually not recommended” (Davidson 1990a, 57). “Groups may organize themselves on the basis of friendship or common interests or they may be carefully composed by the teacher to be heterogeneous with respect to abilities, sex, personality types, race, or other variables” (Dees 1990, 175).
