The purpose of this study was to explore teachers' perceptions of the key supports principals provided that contributed to the development of high-functioning professional learning communities (PLCs). This study used a qualitative case study approach to learn from three schools in one mid-city district. Findings revealed three specific supports provided by school leaders: (1) the communication of clear expectations for PLC work; (2) the provision of school-based professional learning; and (3) a school culture focused on learning and collaboration. Implications for practice at the district and school level, for policy, and for further research are considered.