This mixed methods study seeks to explore the relationships between teacher concerns, self-efficacy, and level of comfort with the implementation of drama-based instruction (DBI) within a large-scale initiative to increase learning opportunities through the arts. This study was embedded in a year-long professional development program during which teachers either (a) attended three school-wide in-service trainings ("non-cadre teachers") or (b) participated in a small group ("cadre teachers") that received ongoing, focused support from a teaching artist throughout the year in addition to the school-wide training. Significant differences were present in cadre teachers' comfort with the reform as compared to non-cadre teachers both at the beginning and end of the reform. Additionally, self-efficacy and comfort with DBI were significantly related at both the beginning and end of the year. Teachers who were more comfortable with DBI appeared to progress to higher order concerns regarding the reform. We discuss the significance of these findings in the context of design and implementation of professional developments that promote pedagogical conceptual change.