Designing infrastructures to support instruction remains a challenge in educational reform. This article reports on a study of one school system's efforts to redesign its infrastructure for mathematics instruction by promoting teacher leadership. Using social network and interview data from 12 elementary schools, we explore how the district's infrastructure redesign efforts were internally coherent with and built upon existing infrastructure components. We then explore relations between infrastructure and school practice as captured in the instructional advice- and information-seeking interactions among school staff, finding that teacher leaders emerged as central actors and brokers of advice and information about mathematics within and between schools. Further, changes in school advice and information networks were associated with shifts in teachers' beliefs about and practices in mathematics toward inquiry-oriented approaches consistent with district curriculum. We argue that the district's redesign efforts to support teacher leadership coupled district curriculum and school and classroom practice in mathematics. (Contains 4 tables and 3 figures.)