What defines an effective school leaderand how do you measure effectiveness? School leaders have a direct and significant impact on student achievement. They drive the effectiveness of teachers who, in turn, influence the performance of students. Without the right kind of support, training, vision, and tools, however, school leaders are often unable to perform at the highest levels of effectiveness. Based on historical and contemporary research, School Leadership for Results: Shifting the Focus of Leader Evaluation explores the importance of evaluating school leaders based on something far more powerful than measurement alone: evaluating based on growth. Education authorities Beverly G. Carbaugh, Robert J. Marzano, and Michael D.