In classroom teaching, material objects like the blackboard play an important role. Yet qualitative research on education has largely ignored this material dimension of education and focused on interaction and discourse. Both dimensions are, however, closely related to each other. Material objects are embedded in classroom discourse and are transformed into knowledge objects by speech acts, and in turn structure discussions and constitute a point of reference for school lessons. Drawing on ethnographic research on classroom lessons in mathematics and science classes in German high schools, we propose a perspective that recognizes both the materiality of teaching and its interactive dimension.