This study investigated the impact of a Professional Development School (PDS) on student learning by comparing student achievement in a PDS and a control school. Student achievement data were collected from an elementary PDS and a matched control school over a 6-year period. The results indicate that the PDS moved more students up to mastery level and more students out of intervention level on state standardized tests than the control school. PDS development descriptions and standards ratings are used to provide a picture of PDS partnership building and a context for the findings. The PDS Standards Student Learning Pyramid is used to interpret the impact of PDS partnership activities on student learning increases. (Contains 6 tables.)