This article provides an integrative review of the extant literature on K-12 student mobility in the United States. Student mobility is a widespread phenomenon with significant policy implications. Changing schools is most prevalent among minority and low-income students in urban school districts. There is an ongoing debate about whether student mobility is helpful or harmful. Earlier research compared movers with nonmovers using cross-sectional data and did not always include controls for the students' prior achievement and demographic characteristics. Studies in the past decade compared movers with themselves over time using longitudinal data and provided more convincing estimates. Overall, switching schools is associated with a negative impact on students' educational outcomes; however, transferring to higher quality schools may offset and outweigh the transition costs of moving. Strong causal claims are elusive due to considerable data and methodological challenges and the inability to account for the motivating reasons for changing schools.