This study describes strategies children use to solve a complex problem. The problem asked children to figure out how to control a “vehicle” that they “drove” by pressing particular keys on a computer. The problem can be viewed as scientific in that variables must be identified and hypotheses formulated and tested to discover cause-effect relationships. Subjects were fifth and sixth graders sampled from public and private schools. The primary purpose of the study was to examine the transition between implicit, immature problem-solving strategies and explicit, mature theorizing characteristic of scientific problem solving. The study manipulated the problem perspective subjects were given and the number of cause-effect relationships in the problem. The study's description of children's problem solving highlights “focusing,” problem-solving behavior that is aimed at forming a mental representation, model, or theory about the problem, as a key link between mature and immature reasoning. Subject's school and school X perspective interaction was found to affect problem-solving performance.