To determine if differing ability levels will affect the acquisition of problem-solving skills and self-esteem as a result of participation in two approaches to teaching problem-solving skills, a study was conducted with sixth graders in a posttest-only control group experimental design. Subjects were 102 sixth graders randomly assigned to 5 classes. Two classes participated in the Creative Problem Solving (CPS) for Kids approach to teaching problem solving. Two classes received computer-assisted instruction in problem-solving designed by the Minnesota Educational Computing Consortium, and one class was a control group. Both approaches consisted of five 3-minute lessons per week for 6 weeks. Results suggest that thinking-skills instruction does impact the development of creative and critical thinking and that the acquisition of these skills has a positive effect on self-esteem. The study also provides evidence that the length of training is an important consideration in providing thinking-skills instruction, and that such instruction should be an integral part of the curriculum rather than a supplementary or isolated program. In addition, thinking-skills instruction is appropriate for students at all ability levels. Seven figures and 12 tables present study findings. (Contains 17 references.) (SLD)