Leadership is second only to teaching among in-school influences on student success, and its impact is greatest in schools with the greatest needs, according to this landmark examination of the evidence on school leadership.

Decades of research, the authors suggest, support the notion that those who seek to improve schools should focus not just on teachers but also on principals and administrators. School leaders should, among other things, be able to set clear direction, establish high expectations, and develop talent in their schools to fully support teaching and learning.

Drawing on both detailed case studies and large-scale quantitative analysis, the authors show that the majority of school variables, considered individually, have at most a small impact on learning. The real payoff comes when individual variables combine to reach critical mass. Creating the conditions under which that can occur—such as a positive school culture combined with appropriate professional development for teachers—is the job of the principal. The study finds that taken together, direct and indirect effects of school leadership account for about a quarter of total school effects.

The authors further suggest that success in the absence of leadership is difficult. The researchers found “virtually no documented instances of troubled schools being turned around without intervention by a powerful leader.”