This text is intended for both the teacher and the psychologist, it was inspired by a practice of teaching and research, at different levels of the school and university curriculum. We present the paradigm shift in psychology that has led from piagétienne theory and cognitive theories to a socio-historical and didactic approach to school learning situations. This orientation is part of a current that develops at the confluence of various disciplines: developmental psychology, sociocognitive psychology, psychology of language, historical and cultural psychology, anthropology, didactics. We will try to show in the line of the great founders that are notably Vygotsky, Wallon and Bruner, how the analysis of the practices and representations of teachers and pupils cannot be satisfied by the mere use of cognitive or neuropsychological models, neglects the historical and cultural dimension of knowledge and the didactic specificities of the production and transmission of this knowledge. It will be for us to present in a historical perspective this epistemological reversal and to propose a definition of the didactic situation. The knowledge at stake is in this case the mathematical problem solving activity at school, we will question the interactive, institutional issues of this activity, for the teacher and for the student. In this socio-historical and didactic perspective, it is not conceivable to consider school activities, apart from the social, institutional and cultural contexts in which they unfold. Knowledge is built in the activity situated, in a process of appropriation dear to Vygotsky, the construction of shared meanings, as the emergence of an intercultural encounter between the learner, the teacher and the knowledge.The first part, based on major founding theories in developmental psychology, presents the scientific revolution that led from piagétien structuralism to the socio-historical perspective. The second deals with cognitive theories of information processing, the piagétien functionalist current, and ...