French curriculum places great emphasis on problem-based learning because scientific problems are supposed to have an essential part in the construction of scientific concepts. For researchers in didactics, the students’ appropriation of scientific problems is necessary to allow them to start assimilating scientific culture and to build knowledge.In this paper, we study how two teachers (a student and an experienced teacher) conduct a phase of problem building involved in acculturation to science.In the analysis of the teachers’ actions during those sessions, we identified two kinds of sequences: times of convergence and times of divergence. During the phases of convergence, the teacher’s actions (through problems building and solving) engage students in a process of acculturation to scientific ways of knowing, whereas during the phases of divergence, the teacher’s actions, even if they stick to the topic, don’t support this process but aim to fulfill other requirements of school teaching. We found that the occasions of convergence were more numerous in the session led by the inexperienced teacher, while those of divergence were more common in the session led by the experienced teacher. Our study tries to identify the differences between the two teachers and to explain their source.< Leer menos