From an organizational perspective, this paper synthesizes research on instructional leadership at the secondary level to provide principals with useful school management models to overcome obstacles to effective supervision. In addition, this paper analyzes the properties of secondary schools that shape principals' work; reviews their daily tasks; describes models of instructional leadership; delineates specific ways that high school principals influence school and classroom processes to shape teaching and learning; discusses how principals build school cultures and foster school improvement; and gives specific instances of the ways some principals mold teaching and learning in suburban and urban settings. Several conclusions emerge from this discussion. First, principals share their instructional leadership position with assistant principals, department chairs, and teachers. Second, instructional leadership in high schools often attends to both the technical side of the school (by configuring and managing the instructional process) and to the cultural side (by molding the norms, values, and beliefs of teachers). Third, principals shape improvement through planned change efforts that incorporate systematic and organized processes that draw on the resources of administrators, teachers, and department chairs. Fourth, principals can cultivate and develop instructional leadership in others. Fifth, principals may exercise instructional leadership through small individual actions. Finally, instructional leadership can be enhanced by fostering a sense of shared clarity of purpose and mission among all school constituents. (JAM)