This presentation focus on of the collaboration between a researcher and a special teacher in a cooperative didactic device to elaborate and bring an instructionnal approach into play to aid a group of students with learning difficulties in mathematics, in primary school. This study comes from an explorative and finished research which takes aim at improving special teacher training. This research takes place in didactics of mathematics (Brousseau, 1986) and is based on a model of the teacher’s action (Sensevy et al., 2000) within the Joint Action Theory in Didactics (Sensevy et Mercier, 2007). This cooperative didactic device is elaborated to permit the researcher and the special teacher to construct together the sessions, so to treat hurdles together. We observed that the researcher took on several roles depending on his proper requirements. He can be sometimes an empathic researcher to listen to the special teacher in interviews, or a researcher and special teacher-expert to guide the special teacher to use a number strip, seldom a didactic engineer to think about the implementation of a mathematic notion (Nedelec-Trohel, 2008). Tardif et Zourhlal (2005) speak about problems of communication between school and university because of their different discursive worlds. According to Bulterman-Boss (2008), is interrogated here “the overlap between the role of the researcher and the role of the teacher” in order to manage to supress it. More precisely, what kind of involvement did (or not) the researcher in the joint thinking about teaching and learning, toward the special section ?

The didactic device is composed of nine sessions about numeration and solving problems for five students about 8-9 years old (third grade). All the sessions and the interviews of the device were videotaped, transcribed and analysed. The researcher (we) coollaborate with the special teacher in order to involve the low achievement students in class activity. We choiced and analysed a crucial moment in the special section when a student made a miscalculation (106 + 10 = 206) not immediately treated by the special teacher. We focuss on of the collaborative interview between the special teacher and the researcher about the preparation of the third session, their way to think over the joint learning games (Sensevy & Mercier, 2007) in situ. To investigate we cross above all the analyses of the transcription and the video of the session with the analyse of the interviews between the special teacher and the researcher.

The researcher didn't succeed in really involving himself in a joint didactic thinking with the special teacher to treat the student's miscalculation. These actors had not the same preoccupation : the teacher was focussing on the students' calculation manner and the researcher on decimal decomposition. The semiosis process shows how the roles of the researcher can create a negative influence on the teacher’s choices (and on the enacted joined learning). Consequently, the didactic device efficiency depends on actors' symmetric status and therefore on the type of research contract established by us. In order to product a most efficient cooperative device (to improve research contract between researcher and teacher and also to feed special teacher training) we elaborated afterward a new organization of our former didactic device with, from the start, a stronger joint didactic studying by the researcher and the teacher about decimal decomposition and then about a special teaching scenario.