Purpose: This study qualitatively examines the efforts of implementing teacher-led collaborative inquiry in American public schools to improve instruction. We focus on a model called Teacher Peer Excellence Group (TPEG), designed to capture the essence of Japanese lesson study and Chinese teaching-study groups that involve lesson planning, peer observations, feedback, and revision.Methods: We conduct qualitative case studies in three pilot schools using a constructivist research paradigm.Findings: We identify action steps essential to introducing and sustaining the TPEG model and pathways to local adaptation.Implications for research and practice: The study contributes to the body of research that seeks to understand the role of instructional leadership and teacher decision-making in successful school-level initiatives.