This comparative case study explores how 18 state education agencies (SEAs) support school districts in advancing standards-based elementary science reform. We identify how SEAs understand their work in advancing elementary science reform and describe how SEAs sought to engage districts in bridging from standards to classroom practice. Based on our analysis, we argue that the school subject is a critical explanatory variable in understanding SEA efforts to support standards implementation and SEAs lean on a resource-based approach for instructional policy implementation. This study contributes to the growing research base on the role of state policy in supporting standards implementation.