1. DESCRIPTION This paper aims at understanding how teachers’discourses facilitate or not students’ learning. We study a biology class at primary school, in order to elaborate a description system of the didactic transactions. We emphasize the teacher’s discursive strategies. Our theoretical frame is the Joint Action Theory in Didactics (Sensevy, Mercier, Schubauer-Leoni, Ligozat, & Perrot, 2005 ; Sensevy & Mercier 2007; Sensevy, 2008. From this theory, we use the notion of didactic reticence, which refer to the following fact. In order to be sure that the student has really learned « by himself », the teacher must remain tacit about the main knowledge at stake.. Another tool we use to characterize the didactics transactions is the teacher’s double come along/analysis position(Schubauer- Leoni, 2005). In the come along position the teacher’s revoicing is very close of the student’s words. The teacher does not show very much his relation to knowledge (and conversely for the analysis position).

2. EPISODE CONTEXT We analyze a specific episode from a videotaped and transcribed biology class (first grade). In the episode at stake, the students were sorting seeds. They had to report and explain their categorization criteria from their observation drawings.

3. RESEARCH FINDINGS The teacher manages the situation by proposing what we may describe as two learning games (Sensevy, 2008): to define the observations drawing criteria and to determine the specific lexicon related to the seeds morphology. In order to manage these learning games, the teacher is going to develop discursive strategies. In the paper, we will show how the teacher vary from a come along position to an analysis position in dealing with the student’s propositions and attitudes, and how he uses of his didactic reticence: in analysis position the reticence is minimum and in come along position the reticence is maximum. Between these two poles, we observed a range of intermediate positions. For the teacher, a way of acting between these two discursive poles consists of moving from strictly paraphrasing students’ utterances to reformulating them. 4. CONCLUSIONS AND EXPECTED OUTCOMES We conclude our paper by proposing a first description system of the teacher’s discursive strategies. We weave together two analysis levels : - At a « micro » level the implementation, for each statement, of the following pattern : Didactic position : (Come along/ Analysis) Didactic Reticence : (degree + ; +-; 0) Revoicing : (paraphrase/ reformulation) - At a « meso » level the identification of specifics learning games. This system description might enable us a better understanding of the joint didactic action between teachers and students, with respect to specific knowledge at stake.