Prevention, intervention, and research efforts are grounded in a belief that teachers should only use alternative educational practices after reasonable evidence has indicated that general education practices implemented with a high degree of integrity have been unsuccessful. To investigate levels of implementation of an evidence-based primary reading program, we observed teachers’ use of Open Court, a commercially-available core reading program, during the district-mandated two-hour literacy block. We found that the amount and type of literacy and language arts instruction children received varied across classrooms. We discuss the implications of our work for future research and the improvement of childhood education practices.