In France, social mixing is at the centre of urban renewal policies, which intend to favour a more balanced coexistence among populations from different social backgrounds. In order to achieve more equitable opportunities in public establishments, school policies aim at introducing more social diversity. This paper questions the effects of these policies in the city of Marseille, traditionally framed by a strong north-south socio-spatial segregation. Drawing from a research on neighbourhoods’ changes related to urban renewal, it discusses the statistic evidence of residential mixing compared to school diversity. The analysis of a school administration’s database, together with interviews of professional educators, unfolds the determinants of school choices. The results indicate that statistical residential mix—which is directly related to the urban projects that contributed to a social diversification—does not lead to more shared schooling practices among residents. Even if the reform in the schools attribution system (“the school mapping”) introduced in 2007 attempted to promote school mix, we observe a rise in practices of avoidance in certain schools sectors. This applies now to more than half of the population. Public schools struggle to socially diversify their student body, unless they engage in selective academic programming, which also tends to move segregation within the schools themselves. Private schools are still used as a main refuge for newcoming residents belonging to the middle and upper classes, and engaged in social reproduction.