This manuscript presents a conceptual heuristic to describe the development of a shared understanding of both collaboration and ambitious mathematics instruction within the context of a school-based improvement initiative. Based on empirical evidence from a two-year study in four elementary schools, we argue that the school community first learned about new ways of collaborating and new ways of teaching mathematics in a technical form, or the "what" of the new approaches, and later utilized the approaches across the school organization and broader conceptions of mathematics in an integrated manner. Key to the improvement was the role of leadership in framing how the technical forms were situated in the broader contexts of both school reform and ambitious mathematics instruction.