This article focuses on the leadership practices that four public school principals in two Northern California large urban school districts used during the process of implementing the state-mandated reading curriculum. These four school principals' leadership approaches are described and analyzed through the lens of neoinstitutional theory to understand how they influenced instructional practices in their schools. The findings of this research suggest that the extent of school principals' instructional, cultural, and political knowledge influenced their actions as agents of bridging and/or buffering.