Research demonstrates "student mobility," or students transferring schools, significantly affects student academic outcomes, making it a critical concern for policymakers and practitioners. Within-school-year transfers, in particular, often reflect sudden, unexpected circumstances. However, research on the prevalence, risk factors, and patterns of student mobility remains limited. This study leveraged an ecological framework to identify student, school, and neighborhood characteristics linked to within-year school transfers and to examine whether these patterns differ across urban and suburban/rural contexts. Using regression modeling with Missouri state data spanning nine years, we examined who and where students moved. The results reveal both expected and novel patterns, such as higher transfer rates among students with unstable housing, special education needs, and in high-suspension schools, with implications for policy, practice, and future research.