Policy makers tend to think that residential ‘mixing’ of classes and ethnic groups will enhance social capital. Scholars criticize such ‘mixing’ on empirical and theoretical grounds. This article argues that the critics may focus too much on neighbourhoods. Mixing within neighbourhood institutions might work differently, we argue, drawing on data from a mixed school in Berlin, Germany. While class boundaries are constructed, we also find class-crossing identifications based on setting-specific characteristics, highlighting the setting’s importance and the agency of lower/working and middle-class parents. Parents create ties for exchanging setting-specific resources: child-related social capital. Institutional neighbourhood settings can hence be important for boundary work and social capital. Criticism of social capital and social mix should not overlook the role of networks for urban inequality.