Purpose: Scholars have focused their attention on systemic reform as a way to support instructional coherence. These efforts are often layered on to existing social relationships between school staff that are rarely taken into account when enacting reform. Social network theory posits that the structure of social relationships may influence the direction, speed, and depth of organizational change and therefore may provide valuable insights in the social forces that may support or constrain reform efforts. This study aims to discuss this issue. Design/methodology/approach: This mixed-methods exploratory case study examined five schools within one under-performing school district as it enacted a system-wide reform. Quantitative survey data were collected to assess social networks and teacher work perception of five schools enacting the reform. Qualitative data were gathered through individual interviews from educators within representative grade levels as a way to better understand the diffusion and implementation of the reform. Findings: Despite being enacted as a system-wide reform effort, the results suggest significant variance within and between schools in terms of reform-related social networks. These networks were significantly related to the uptake, depth, and spread of the change. Densely connected grade levels were also associated with more interactions focused on teaching and learning and an increased sense of grade level efficacy. Practical implications: The findings underline the importance of attending to relational linkages as a complementary strategy to the technical emphasis of reform efforts, as social networks were found to significantly facilitate or constrain reform efforts. Implications and recommendations are offered for leadership, policy and practice that may support the design and implementation of reforms, which may ultimately increase student performance. Originality/value: The study makes a unique contribution to the reform literature by drawing on social network theory as a way to understand efforts at reform. The work suggests that the informal social linkages on which reform is layered may support or constrain the depth of reform. (Contains 4 tables, 4 figures and 1 note.)