Findings of a study that examined the relationship between variations in patterns of school leadership and group problem-solving process are presented in this paper. Interviews were conducted at the beginning and end of the school year with 12 principals in British Columbia who had implemented the Primary Program. The initiative was designed to restructure the first 4 years of schooling through such organizational changes as ungradedness, continuous progress, dual-entry periods to kindergarten, and active student participation in learning. Findings indicate that principals who engaged in both indirect and direct forms of instructional leadership demonstrated significantly higher levels of group problem-solving expertise than did building-centered and teacher-centered managers. This suggests that the thinking that gives rise to instructional leadership practices is similar to the thinking that creates an expert collaborative problem solver. Second, differences among principals in 10 dimensions of group problem solving were most evident in principals' purposes, skills and knowledge, and dispositions. Finally, the most effective forms of leadership were associated with women who had limited formal experience as principals. An implication is that administrator preparation curricula should be organized around a grounded view of the principal's world. Four tables are included. (Contains 44 references.) (LMI)