The objective of this article is to reflect on how teachers from the teams of the FEBEM SP teams develop their social-psychological evaluations, which define the situation of the children and adolescents attended by the institution. The ambiguous, arbitrary and inefficient roles of this technical task within the juridical-institutional mechanisms for the social and educational care of these individuals will be emphasized. The theoretical framework prioritizes a sociological focus in diagnostics based on the work of Robert Castel, and then approaches diagnostic practice based on the interactional theory of deviation and on the study of representation. This analysis will be illustrated by the discourse of the team professionals, in which the diagnostics appear to come from ideas that they have of the children and adolescents of FEBEM and from their practice itself. In its totality, this text makes the fragility of written reports explicit. This is a result of institutional functioning and the subjectivity of the specialists, making improvement in the quality of care at the FEBEM difficult.