This article presents the results of an 11-year longitudinal study of the impact of America's Choice comprehensive school reform (CSR) design on student learning gains in Rochester, New York. A quasi-experimental interrupted time-series approach using Bayesian hierarchical growth curve analysis with crossed random effects is used to compare the annual gains in test performance of students attending America's Choice schools to those of students attending other Rochester schools and to those of students attending America's Choice schools before they adopted this CSR model. Findings reveal significant annual effects, which accumulate over time, in elementary and middle grades reading and mathematics. (Contains 6 tables, 7 figures and 9 notes.)