Wherever there is a system of social stratification, there is a corresponding differentiation within the educational system this is the case even in some primitive societies; the Maori, for example, had commoners’ schools during the winter, but also ‘sacred colleges’ which were open only to the nobility, especially the elder sons of chiefs. In most literate societies, literacy has been limited to the upper social strata. Modern industrial societies, which established mass literacy for the first time, did not by this means remove the educational distinctions between different social strata. These were maintained by the existence of different types of schools for the various social groups, such as the English ‘public schools’, reserved for children of the upper class, or by the unequal distribution of opportunities for higher education.