A growing body of research evaluates the effects of turnaround on chronically low-performing schools. We extend this research to formally test factors that 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 highly effective teachers and employing effective principals partially explain positive effects of iZone interventions. In the ASD, high levels of teacher turnover suppress potential positive effects after the first year. In iZone schools, several factors suppress even larger positive effects: hiring more novice teachers; hiring more principals with less experience; and high levels of student chronic absenteeism and student in-migration.