This article explores the transition between levels of schooling as a process in which students are moved between organizations. It focuses on a structural aspect of the transition process: students' patterns of movement from middle schools to high schools, which differentially affect students' academic adjustment to high school, depending how well the students were doing academically in middle school. Students who excelled in middle school seem to benefit from attending the same high school as a majority of their eighth-grade classmates, but those who are struggling academically seem to benefit from enrolling in another high school. Thus, institutional processes of schools affect students differently, depending on their positions in the educational hierarchy, and provide varying opportunities for structural mobility within the stratification systems of schools.