The aim of this paper is to analyse certain techniques of subjectivation in modern child-rearing and the way in which medical discourse leads to the construction of children through those techniques. As a case study, several manuals on childcare used during the first third of the twentieth century in Spain and France have been selected. A historical-genealogical perspective is adopted, according to which childhood is not a natural or ahistorical category, but depends on cultural practices. In Western countries, these practices have been strongly influenced by expert discourses. The techniques proposed in the manuals are identified and the theoretical justification for them analysed according to the socio-cultural and historical context. It is shown in what sense the practices recommended by doctors for mothers constituted a kind of early informal education contributing to the creation of future well-educated citizens.