Using survey responses from a national sample of US teachers, this paper provides insight into 2 questions: (1) Do 3 specific attributes of leadership behavior--the sharing of leadership with teachers, the development of trust relationships among professionals, and the provision of support for instructional improvement--affect teachers' work with each other and their classroom practices? and (2) Do the behaviors of school leaders contribute to student achievement? We tie this investigation of school leader behaviors to 2 additional factors that have also received increasing attention in research because they have been shown to be related to student achievement: professional community and the quality of classroom instruction. Our analysis provides an empirical test of the notion that leadership variables are positively related to student learning. It also suggests that both shared and instructionally focused leadership are complementary approaches for improving schools. (Contains 4 tables, 1 figure, and 9 notes.)