Background: This study addresses the nexus of two significant yet under-researched areas of instructional leadership: the role of central office administrators in developing principals as instructional leaders and the potential for the instructional leadership team (ILT) to serve as a structure for supporting administrators and teachers in working collaboratively to improve instruction and student learning in their schools. Purpose: Specifically, this study examines the efforts of principal supervisors--central office administrators responsible for supporting and evaluating principals--who aimed to develop instructional leadership broadly in high-poverty high schools by leading professional learning opportunities for principals and members of their ILTs. Participants: Participants included principals and ILT members (e.g., assistant principals, teachers) in three high-poverty high schools in the same urban district and the three principal supervisors responsible for supporting them. Research Design: Drawing on 36 interviews and approximately 80 hours of observation of ILT meetings and professional learning opportunities, the present study uses in-depth case studies of three focus schools to identify the specific practices principal supervisors use to influence the work of principals and ILTs. Findings: The findings suggest that principal supervisors contributed to ILTs' increased focus on instruction and encouraged principals to share leadership with teachers. Principals and ILT members viewed the support of principal supervisors as most helpful when they engaged in explicit teaching about the purpose and practices of ILTs, approached their work with principals and ILTs as joint work, and shared specific models that could be integrated into ILT meetings. Conclusions: The practices used by principal supervisors represented a significant shift in the role of central office administrators toward a focus on teaching as opposed to a more traditional focus on supervision.