Action research improves teaching practice, builds teacher leadership skills, and supports student learning. Moreover, professional development schools (PDS) and other school-university collaborations are positioned to provide built-in guidance and support for P-12 teacher-researchers. This article provides an overview of 12 action research projects that comprise the special issue of School-University Partnerships themed "The Impact of Teacher Leadership on Student Learning in Professional Development Schools." The themed issue provides action research models and inspiration for teacher-researchers, a starting point for teacher leaders and college/university faculty, and impetus for writing up action research for scholarly presentation and publication. [ABSTRACT FROM AUTHOR]