This Article establishes links between what became known as the “paradigm crisis” in the Sociology of Education (SED) in the 90s and the emergence of the Children’s Sociology (SI), which proposes a new paradigm for social studies in childhood. At the heart of this new paradigm are the principle of the social construction of childhood, that of the child actor and the demand for the conceptual autonomy of childhood (or ‘epistemological citizenship of the child’). The initial distance between SED and SI was based on the fact that SED had always focused on macro relations between school and society, both in its structural-functionalist and in the context of reproduction theories. In this context, the ‘children’s letter’ and the ‘pupil’s letter’ have a complex existence which helps to understand theoretical and methodological constructions within these subjects and their tense links. Keywords: Sociology of education; Children’s sociology; Pupil’s letter; Children’s letter.