Researchers from Mid-continent Research for Education and Learning (McREL) have analyzed thousands of quantitative studies published over the last 30 years to determine what works in classrooms and in schools. In two earlier meta-analyses, McREL identified teacher and school practices that have the largest effects on student achievement. McREL has completed a third meta-analysis of the effects of school leadership on student achievement. The authors assert the strength of this relationship and provide straightforward and compelling guidance to superintendents, principals, and others responsible for improving school performance. (Contains 6 figures and 2 resources.)