How the situation seeds used in adapted lesson studies support the collaborative work of facilitators and future facilitators

International audience ; Our ongoing research investigates the role of situation seeds in the collaborative work and professional development of facilitators and future facilitators involved in LSa, an adaptation of Lesson Studies. More precisely, in this paper, we study the emergence and circulation of mathematical and didactic knowledge in the collaborative work carried out during the development of a particular situation seed by facilitators and its use in LSa designed to train new facilitators. To this end, we rely on the Three-Tetrahedron Model (3T-Model) proposed by Prediger et al. (2019) and the MTSK model of teachers' knowledge (Carillo et al., 2018). This paper presents and discusses the first results obtained.