Drawing upon the case of slums and transit camps in post-war Nanterre, France, this article focuses on the relations between spatial socializations and upward mobility. These residential spaces socialized children and teenagers to a triple border that is urban, social, and racial. But because of the work of activists from the outside, these dynamics were disrupted and socialization processes that encouraged upward mobility took place. Family portraits also illustrate how these socializations affect trajectories depending on family resources and migratory aspirations (and secondarily on sex and generation).