The last 5 years have witnessed growing support amongst government institutions and educational foundations for applying continuous improvement research (CIR) in school settings. CIR responds to the challenge of implementing effective educational innovations at scale by working with practitioners in local contexts to understand ''what works, for whom, and under what conditions.'' CIR works to achieve system improvement through the use of plan-do-study-act (PDSA) cycles, which are multiple tests of small changes. This comparative case study of two urban school districts examined how innovation design teams took up PDSA in their work to improve high school student outcomes, and their perceptions of PDSA as an approach to innovation development, adaptation, and implementation. Findings revealed both possibilities and challenges for implementing PDSA. Nearly all participants reported the value in PDSA, and participants pointed to "connections to previous experiences" and "PDSA training" as helping to build capacity. However, we found mixed levels of enthusiasm for actually conducting PDSA cycles, and capacity constraints regarding time and data collection. [This article was published in "Journal of Educational Change," (EJ1157388).]