The central question for this study is whether the improvement of group instruction can increase achievement to the same level as or even higher than that produced by the feedback-corrective process used in mastery learning. It is hoped that the findings can be of interest to developing countries. (RL)

When instruction is weak and inappropriate to a goal, only students with high intelligence and aptitude learn rules for problem solving. All students learn, when given time, help, and opportunity to practice problems. (RL)