In this research we offer empirical evidence that disciplinary identity is a factor in the training of students in mathematics teaching. We show, with the Socioepistemological Theory of Mathematics Education, how this factor intervenes in the resignifications of mathematical knowledge and in the definition of the mathematics teacher function. The source of analysis was found in the student’s school-academic setting accompanied by the development of the vision of teaching and mathematical knowledge that is building on the permanent habit of school activity designs. Using ethnographic methods and semi-structured interviews, immersions were conducted with communities of students who are being trained in teaching. As a result of the research it was found that in the permanent habit of designing school activities is the source of meaning that defines the disciplinary identity.