All large high schools have teachers in middle tier roles who help run the school, and subject leaders (SLs) who engage in administrative and pedagogical practices to improve departmental achievements. By applying structuration theory (Giddens, 1984. "The constitution of society: Outline of the theory of structuration." Berkeley, CA: University of California.) we seek to understand how rules, resources, and structural position enable SLs to contribute to school effectiveness. A multi-case study method was employed to study 12 SLs from two effective schools and two less effective schools. Interviews, observations, and document analysis served as data collecting tools. The findings indicate that all the SLs engage in administrative practices but in different ways. The SLs in the less effective schools devoted much more time to such practices and much less to pedagogical practices than the SLs in the effective schools, which provided clearer rules and sufficient resources. We conclude that on the pyramid of school needs, administrative practices are more basic for school effectiveness, and only after this is achieved can SLs devote time to satisfy pedagogical needs. However, the ability of SLs to satisfy administrative needs depends to a large extent on the principal providing them with the necessary rules and resources. Further theoretical and practical implications are discussed.