This paper reflects on the use of didactic material in mathematics classes. It focuses on the mathematical activities of students and the didactical activities of teachers. Its point of departure is a critique of technical-managerial approaches to teaching, learning, and innovation. Based on this critique, fundamental tensions between the development of new didactic material and the cognitive style and daily routines of practising teachers are identified. In the last part of the paper, the concept of mathematical literacy is introduced in order to set the crucial relationship between didactic material for mathematics instruction and the ways in which it is used in the classroom on new and fertile grounds.