The aim of this article was to determine the factors in teachers' actions that could explain differences in the emotional atmosphere of primary school classrooms. Based on pupils' drawings about their mathematics lessons, we analyzed both the pupils' and their teachers' actions, including pupils requesting help, sitting alone, and talking about mathematics, as well as the teacher helping, praising and criticizing. We could conclude that the teacher has a central role in the formation of the emotional atmosphere in mathematics lessons. The emotional atmosphere can be built up to be positive when the teacher encourages the pupils to talk about mathematics and their own understanding with each other. The emotional atmosphere is then open and tolerant. The emotional atmosphere can turn to be negative when the pupils are working by themselves and are afraid of criticism and embarrassment.