The paper uses a semiotic lens to describe the teacher’s interventions in classroom discussions, with all the students or only o group of them. The frame is semiotic-cultural and considers teacher’s production within students’ productions, during the development of a mathematical activity. This frame uses the model of the semiotic bundle to describe the various semiotic contributions (by the teacher and the students) and allows focussing some important strategies, called semiotic games, used by the teacher to support students’ mathematics learning.