A significant proportion of pupils move school during their school career for reasons other than standard structural moves between educational stages. Little is known about the underlying causes of these moves and the characteristics and experiences of mobile pupils are challenging to research. There is currently a large disconnect between the macro level of system structures, data and policy and the individual experiences and journeys of mobile pupils. This article brings together international literature around school mobility and mobile pupils, with analyses of the English National Pupil Database (NPD), tracking a cohort from age 5 to 16, to better understand when school moves occur and the characteristics of mobile pupils. Findings reveal a sizable underlying rate of moves in England of about 1.5-2% per term and identify differences in mobility related to disadvantage, school phase, ethnic group and SEND status. The predictive power of the data, however, is low, highlighting the need for more research, policy and practice in this area to better understand individual mobility circumstances. By bringing together the literature and the data, the article concludes with a discussion of what is known about school mobility and recommends further areas for research into the characteristics, experiences and outcomes of mobile school pupils.