This paper reports on a study investigating the effects of studying alone or in cooperative-learning groups on the performance of high and low achievers. The effects of completing computer-based instruction using either learner or program control are also examined. A total of 92 sixth-grade students were classified by Stanford Achievement Scores and randomly assigned to group or individual treatments, stratified by achievement scores. Students completed training to enhance small group interaction before completing the computer-based tutorial and posttests. Both high and low achievers in the cooperative treatment increased achievement on program-controlled and learner-controlled computer lessons. The learner-controlled cooperative learning group made more options while checking their concept learning and spent more time interacting with the learner-controlled, computer-based tutorial than the learner-controlled individual learning group. Six statistical tables are appended. (Contains 13 references.) (Author/KRN)