Abstract
The intensity of between-school pupil mobility in Flemish regular primary education is measured for the first time, using enumerative data about a birth cohort. Given the lack of internationally established measures, several indicators representing the system’s, the pupil’s, and the school’s point of view are introduced. It turns out that the level of mobility is significant, as compared to other atypical events in pupils’ trajectories. The consequent importance of mobility as a nuisance factor in education research is discussed. The under-researched issue of school definitions is shown to have an impact on mobility measurement in Flanders and is discussed from the wider perspective of effectiveness research. Directions for future research about between-school pupil mobility are set out.