The persistence of underperformance in schools within large urban districts remains a significant challenge in the U.S. K-12 education system. Education policymakers have enacted legislation aiming at improving these schools through "turnaround" initiatives. However, students attending underperforming schools face multifaceted challenges that extend beyond the classroom. Therefore, restructuring the underperforming schools without addressing critical out-of-school factors appears to be insufficient to achieve the goal of these legislative efforts. In this study, we focus on a large urban school district in Massachusetts with many underperforming schools undergoing school turnaround. During the turnaround process, some schools implemented a comprehensive student support intervention while others did not. The variation in supplementing school turnaround with comprehensive student support intervention and the timing of the implementation of the intervention allows us to explore whether comprehensive student support aiming at addressing out-of-school factors enhances student performance during the school turnaround process. Employing difference-in-differences and event studies research designs, our findings reveal that schools and grades implementing the comprehensive student support intervention during their turnaround efforts demonstrate improvement in math and English language arts compared to those not implementing the intervention. These results provide valuable insights for policymakers, emphasizing the essential role of comprehensive student support in enhancing the success of school turnaround.