The impact of school mobility on the academic achievement of students has been studied as early as 1935. While prior researchers have included demographic variables in school mobility studies, they have not examined the impact of school moves in conjunction with changing school-level socioeconomic status (SES) on the educational outcomes of children. Using nationally representative data from the Early Childhood Longitudinal Study (Kindergarten cohort), the author evaluates the influence of school transitions on the reading skills of several million children who attended kindergarten through fifth-grade in the U.S. A two-group latent growth curve model is used to estimate the impact of school moves on the growth of reading skills across time. The study includes time-invariant and time-varying variables at the level of the individual and the environment. The results should shed some light on the varied impact of changing schools on the reading skills of poor and non-poor children within and across race, controlling for age, gender, school level SES, mother's level of education, and family structure of the children.