Purpose: The purpose of this study was to examine the relative impact of different types of leadership on students' academic and nonacademic outcomes. Research Design: The methodology involved an analysis of findings from 27 published studies of the relationship between leadership and student outcomes. The first meta-analysis, including 22 of the 27 studies, involved a comparison of the effects of transformational and instructional leadership on student outcomes. The second meta-analysis involved a comparison of the effects of five inductively derived sets of leadership practices on student outcomes. Twelve of the studies contributed to this second analysis. Findings: The first meta-analysis indicated that the average effect of instructional leadership on student outcomes was three to four times that of transformational leadership. Inspection of the survey items used to measure school leadership revealed five sets of leadership practices or dimensions: establishing goals and expectations; resourcing strategically; planning, coordinating, and evaluating teaching and the curriculum; promoting and participating in teacher learning and development, and ensuring an orderly and supportive environment. The second meta-analysis revealed strong average effects for the leadership dimension involving promoting and participating in teacher learning and development and moderate effects for the dimensions concerned with goal setting and planning, coordinating, and evaluating teaching and the curriculum. Conclusions and Implications for Research and Practice: The comparisons between transformational and instructional leadership and between the five leadership dimensions suggested that the more leaders focus their relationships, their work, and their learning on the core business of teaching and learning, the greater their influence on student outcomes. The article concludes with a discussion of the need for leadership research and practice to be more closely linked to the evidence on effective teaching and effective teacher learning. Such alignment could increase the impact of school leadership on student outcomes even further. (Contains 2 tables, 1 figure, and 4 notes.)