There is currently a lack of studies exploring how transport investments and school admission policies in a city can affect the distribution of accessibility to schools. The aim of this study is to investigate if, for whom, and the ways in which, accessibility to schools can change following (1) a change to the city’s public school admission policy and (2) investments in public transport infrastructure and adjustments to the public transport system. We draw on the case of Malmö, Sweden to examine the potential effects of these changes. This study is focused specifically on those in grades 7–9 (aged approximately 13–15), a group whose independent mobility is starting to take form. A geospatial analysis was carried out in order to compare the change in demographic makeup between school catchment areas (real and hypothetical) before and after the changes were made. The geospatial analysis utilises a cumulative opportunity accessibility model that takes into account typical public transport travel times both before and after these new measures were implemented. Findings indicate that the (hypothetical) school catchment areas have been redistributed to a considerable extent following both interventions, but particularly following the change to the public school admission policy. These redistributions have in turn resulted in changes in the socio-economic characteristics of the hypothetical school catchment areas. While the redistribution of school catchment areas could potentially change the socio-economic composition of schools in Malmö, the effects are not equally distributed throughout the city. While the addition of the new train line was the main focus of this study, it was found that other changes in the public transport system between 2018 and 2019 also played a role in determining which schools students could and could not access. The findings from this study highlight the importance of carefully considering the interaction of different effects when assessing policy alternatives.