The concept of dialectical inferences was proposed by Piaget to interpret the inferences arising in the coordination of meanings within the construction of cognitive novelties in physical and logicalmathematical phenomena. First, the different uses given to the concept of dialectics in Piagetian work will be analyzed, emphasizing the original meaning of the term "inferential dialectical". Second, the results of a study on the construction of children's ideas about the right to privacy at school will be analyzed using the category of dialectical inferences. This study was based on interviews with thirty children between 7 and 12 years old living in the Autonomous City of Buenos Aires (CABA) to study the development of their ideas about this right. At the same time, we observed the school practices in which these children participate to characterize how students' personal information was treated at school. Thirdly, we propose a discussion on the construction of social knowledge, identifying the constructive activity of subjects and at the same time the peculiar interactions they sustain with social practices from which the object of knowledge is cut out.