A growing body of research evaluates the effects of turnaround on chronically low-performing schools. We extend this literature by formally testing factors that may either mediate or suppress the effects of two turnaround initiatives in Tennessee: the Achievement School District (ASD) and local Innovation Zones (iZones). Using difference-in-differences models within a mediational framework, we find that hiring effective teachers and principals partially explains positive iZone effects. In the ASD, high levels of teacher turnover suppress potential positive effects. Also, in iZone schools, increased levels of student mobility and chronic absenteeism suppress potentially larger positive effects. Policies that increase capacity within turnaround schools, such as financial incentives for effective staff, appear to be important ingredients for realizing positive effects from turnaround reforms.