Student mobility is highly prevalent in the United States and has negative impacts on students' academic performance. Within-year mobility may be especially disruptive. However, research on the impacts of within-year mobility is limited, and less is known how impacts may vary across different geographies, such as differences between urban and suburban/rural areas. Thus, this study leverages longitudinal student-level data collected over nine years across five large counties with diverse geographic characteristics to investigate how within-year school mobility impacts academic performance over time. Using random-effect panel regression models results indicate that within-year mobility predicted significant declines in academic performance the following year. However, transferring to higher-performing schools initially led to poorer performance, with gradual improvement over time. Findings suggest that school context does matter. We provide implications for policy and practice.