Policy makers have struggled to find successful approaches to address concentrated, persistent low school achievement. While NCLB and the School Improvement Grant (SIG) program have devoted significant time and attention to turnaround, very little empirical evidence substantiates whether and how these efforts work. This study employs a comparative interrupted time series (CITS) to examine a sample of 20 Ohio schools that participated in a school turnaround program and finds participating schools experienced meaningful improvements in student achievement after completing the 2-year program, which persisted and grew in the 2 years subsequent to the completion of the program. Improved student achievement is not wholly concentrated within specific performance categories, suggesting that participation in the program is associated with increases in overall student performance rather than focusing only on students at the margin of proficiency. These results provide some of the first causal evidence of the potential efficacy of focused school improvement efforts.