Background/Context: Though change is constant in organizations, determining how to successfully implement planned change has been a perennial challenge for both organizational scholars and practitioners. While the empirical knowledge base on planned change in schools and other organizations offers numerous insights, the inattention to activity, or the practice of leading and managing change, remains. Organizational change theory, and specifically organizational routines, offers a useful lens with which to examine planned change in work practice in schools. Purpose: The purpose of this study is to understand the role organizational routines play in changing school work practice. Research Design: We employed a longitudinal case study of leadership practice at Adams, a K-8 urban school, over the course of four years. We spent 90 days collecting observations, interviews, and artifacts from a wide range of individuals (e.g., teachers and administrators). We identified one key routine, the Five Week Assessment Routine, and analyzed the ostensive and performative aspects of the routine, identifying similarities and differences in the routine over time. In addition, we identified two different kinds of change, planned and unplanned, as well as the reasons why participants changed the routine. Conclusions: Organizational routines structure work practice, stabilizing it over time, even in the face of considerable change. They represent one mechanism for sustaining leadership. In addition, routines can be a source of both episodic and continuous change in the work place. New routines can serve as a mechanism to build instructional coherence, internal accountability, and professional community. This account suggests that one way to change norms and culture in an organization is through the design and implementation of new routines. Leaders can create opportunities for change in school practice. By designing and supporting an organizational routine, the leaders at Adams focused the practice of the faculty on improving teaching and learning in ways they had never done before. The case of Adams demonstrates that in the enactment of a routine, school staff can also create change in practice. How they make sense of the routine, and integrate it into their practice, can create shifts in teaching and learning. Change happens in the interplay between individual agency and the structure of the routine. Through a case study of one organizational routine in one school, we analyzed how organizational routines can enable both change and constancy in school practice.