Our work focuses on the theme of professional knowledge mobilized by teachers in their lesson preparations and implementation in class. Our study takes place in the context of the teaching of experimental sciences. We study the knowledge of teachers and the evolutions of this knowledge. Our theoretical approach articulates science education and professional didactics; it also retains, for the analysis of teachers' knowledge, the concept of PCK (Pedagogical Content Knowledge). We have developed a specific methodology, involving the researcher and teachers organized in pairs, to observe the gap between the preparation of lessons and their implementation. From this gap, we define critical incidents: they are the basis of the corpus that we analyzed. We identify the knowledge involved, and we indicate how the concept of PCK articulates with the concept of scheme. When teachers use inquiry-based science teaching (IBST), they mobilize specific knowledge and they implement different practices, depending on their work at primary or secondary school. We show that there is a relationship between knowledge and retroactive control that allows the teacher to adjust his/her preparation. We propose a theoretical model, for a form of acquisition of professional experience.
