Purpose: This study provides an analysis of professional development school (PDS) dissertation research that focuses on learning in PDSs. These 103 dissertations written between 1990 and 2020 address an aspect of learning in PDS work, including inquiry as a pedagogical learning tool, student learning PK-12, intern/teacher candidate learning, university teacher educator learning, and inservice teacher learning. From the current exploration of PDS dissertations, most especially from the comparison studies, the authors have learned that there is still no clear path to presenting PDS as having a positive impact when compared with non-PDS experiences.. Design/methodology/approach: Within each of these categories, the authors examine the dissertations by methodology and explore common themes among dissertation findings. As the PDS movement enters its third decade of inquiry and builds its efficacy on models of learning, the findings provide insight into the degree to which PDS scholars are building on the past to determine future PDS research agendas around learning. Findings: The authors examine the dissertations by methodology and explore common themes among dissertation findings. The themes included: intern learning does happen in PDS sites; PDSs provide structures for intern learning; teacher educators can learn from their PDS work; dissertations in the area of student learning overwhelmingly had inconclusive findings, except for research that focused on targeted interventions, which demonstrated student gains. Research limitations/implications: With fewer PDS-focused dissertations being written in more recent years, the authors wonder if the complexity of PDS may be a deterrent to the growth and sustainability of this model? Practical implications: From the current exploration of PDS dissertations, most especially from the comparison studies, the authors have learned that the authors still do not have a clear path to presenting PDS as having a positive impact when compared with non-PDS experiences. However, the authors are beginning to understand the types of studies that are needed to move this agenda forward and hope the work will help inform the PDS community of some. Originality/value: This is the first known study of PDS dissertations across time.