Why did families from the working and lower middle classes prolong the studies of their sons beyond the age of 12 (the end of compulsory schooling) in écoles primaires supérieures and cours complémentaires between 1910 and 1950? This paper, grounded on a 1970s survey of former French male students, aims to reveal the different meanings of such continuing education, often classified under the non-specific category “social demand” in these surveys. Contrary to what has generally been assumed since 1960, only a not so large fraction of the families had a clear aim of social mobility for their sons. For many of the families, the main aim was only a vaguely defined moderate improvement of economic conditions: less physically demanding jobs, better job security and access to stable jobs in administrations or large companies when the family business was reserved for another child or when its decline was anticipated. The advice of teachers and of school principals was often decisive as some parents were originally reluctant to accept the prolongation of schooling, as well as the award of a scholarship at age of 12. The same was also true later in their academic studies, which were often encouraged by teachers and administrators and an acquired taste for studying.