Résumé
In the continuity of our previous research on the impact of teaching practices on the variability of learning among students, we present a first step in order to investigate teachers' discourse more deeply. We identified crucial issues, including linguistic ones, in the conceptualization of line symmetry, related to logical aspects of the concept. This exploratory study consisting in the analysis of textbooks content and some classroom sessions suggests that these learning issues are globally hardly considered but that there are some differences in the ways teachers address them, which are likely to have differentiating impacts on students' learning.