An examination of middle schools in the Canton of Zürich between 1830 and 1980 shows clearly how, within the frame of waves of educational expansion, the participation of various social groups changed: women, rural residents, Catholics could compensate their participation in middle schools to equal that of men, urban residents and protestants. This is not the case for children of lower socio-economic social classes as well as coinciding nationalities. They remain the major disadvantaged group in the middle schools of Zürich Underlying this conclusion, the question arises as to why the discussion of equal social opportunity has been exhausted even though the demands are not fulfilled.