This report details how charter schools are increasingly run by private, nonprofit management organizations called charter school management organizations (CMOs). The researchers find that most CMOs serve urban students from low-income families, operate small schools that offer more instructional time, and attract teachers loyal to each school’s mission, based on survey data and site visits. The authors conducted an impact analysis focused only on middle school grades, finding that a small fraction of CMO-run middle schools boosted achievement growth at notable levels. But on average, student performance in the CMO-run schools did not outpace achievement growth in other charters or in host districts for a statistically matched set of students. This review finds that the report offers an objective assessment of the comparative benefits for middle-school students of a highly select set of CMOs. It also helps to identify organizational features that operate in successful CMO-run schools that are modestly associated with stronger student growth in the middle grades. However, the authors downplay aspects of their methodology that resulted in significant selectivity concerning which CMOs were studied, raising questions regarding the population of charter schools to which they hope to generalize.