The aim of the study was to assess the scale of various interrupted schooling trajectories among Polish youth, and to identify the differences and similarities between students following these trajectories and their reasons for interrupting education. In a dataset of 5,414 young Polish adults, we identified 343 (6.3%) learners who left upper-secondary school at least once and followed one of four interrupted schooling trajectories: school non-completion, school switching non-completion, school switching completion and ISCED 3 graduates' non-completion. They differed from non-interrupted learners in the type of first attended upper-secondary school, gender and socio-economic status, although the pattern of differences varied depending on the trajectory. We also observed differences between interrupted trajectories in the above-mentioned characteristics, as well as in reasons for leaving or switching school, which gives evidence of heterogeneity among interrupted learners. This heterogeneity appeared also in groups usually analysed together, such as early school leavers, which should be taken into account in future studies. Moreover, the analyses showed important similarities between the school non-completion trajectory, which is usually covered in studies, and the ISCED 3 graduates' non-completion trajectory, which to date remained unrecognised. The results served as a basis for policy recommendations.