This essay try to examin teaching and learning situations around circulatory system in primary french school (level 6) with the purpose to infer factors which could give determination of them. We do didactic analysis in Joint Action Didactic Theory (Sensevy and Mercier, 2007) who modelise human action in didactic situation like a set learning games. We have to understand some of games déterminants : teacher relationship to knowledge, practic epistemology and adressed activity. The research offer to continue student determinants exploration inspecting student relationship to knowledge and student knowlegde approach (Charlot, 1997). For that, we do bottom up analysis of joint practices in three clasrooms (CM2) with three teachers of contrasted initial background : a psychology background, a litterary and a scientific bakground.Results show a very important complexity of teacher determinants on account of very closely interlinked bundle of determinants who let more or less space in the classrooms for expression and taking into consideration students relationship to knowledge. Student impact on joint action by relationship to knowledge varies among knowledge approach. Those elements can give a better understanding of classroom practices and suggested some indications for training teachers and to focus on teacher practices evolution.