We examine the Los Angeles Unified School District's Public School Choice Initiative (PSCI), which sought to turnaround the district's lowest-performing schools. We ask whether school turnaround impacted student outcomes, and what explains variations in outcomes across reform cohorts. We use a Comparative Interrupted Time Series approach using administrative student-level data, following students in the first (1.0), second (2.0), and third (3.0) cohorts of PSCI schools. We find that students in 1.0 turnaround schools saw no significant improvements in outcomes, whereas students enrolled in 2.0 schools saw significant gains in English Language Arts in both years of the reform. Students in 3.0 schools experienced significant decreases in achievement. Qualitative and survey data suggest that increased support and assistance and the use of reconstitution and restart as the sole turnaround methods contributed to gains in 2.0, whereas policy changes in 3.0 caused difficulties and confusion in implementation, leading to poor student performance.