Description This presentation focus on a study of teaching practices for students with learning difficulties in primary school. Our research takes place in didactics of mathematics (Brousseau, 1986) and is based on a model of the teacher’s action (Sensevy et al., 2000 ; Sensevy et al., 2005) within the Joint Action Theory in Didactics (Sensevy et Mercier, 2007).

We (as a researcher) constructed two didactic devices with a special teacher and an ordinary teacher to elaborate and bring an instructionnal approach (9 and 10 sessions) into play to aid a group of students in mathematics, about 8-9 years old (third grade). The sessions and interviews (between the researcher and the special teacher ; between the both teachers), were videotaped, transcribed and analysed. We elaborated short classroom design articuled in three phases : firstly, in the special section, the special teacher works on of no-acquired pieces of knowledge ; secondly, in the special section, the students work on by anticipating new pieces of knowledges ; at last, the students diffuse in their class the new pieces of knowledge to their peers, in order to foster a debate. So, in this session of dissemination, what are the teaching techniques of the both teachers to aid these low achievement students to fill their learning gaps ? Do students transmit their new knowledge to their peers and how do they do it ?

Research finding We focuss on the collaboration between a special teacher and an ordinary teacher about the preparation of the session of diffusion in class (coordination of both content, intentions and processes, Clark, 1996) in class and their way to think of their joint learning games (Sensevy & Mercier, 2007) in situ. There was a consensus between the two teachers to organize the dissemination and to conduct the teaching. Low achievement students transmitted their knowledges to peers but there was no debate about it. We think the consensus is not the only condition to manage such a diffusion device. Then, we throw a light on the collaboration between the researcher and the special teacher. It shows us that its efficiency depends on the type of research contract established by the researcher with the both teachers and his involvment during the collaboration. In fact, the researcher uses several roles depending on his proper requirements : he is an empathic researcher during the interwiews but sometimes, he can become a special teacher expert to guide the special teacher in adaptation, or he can be a teacher trainer to help him. And, at the moment of the scientific analysis, he becomes a researcher stricto sensu to define these complex roles. This semiosis process shows how these different roles of the researcher can create a positive or a negative influence on the teachers’ choices (and consequently on the enacted joined learning) to involve students with learning difficulties in mathematics in class activity.