This article considers the emergence and meaning of a particular kind of surveillance in classrooms: the one represented by the gaze of the teacher. Drawing on teaching manuals and other normative material published between the 1820s and the 1960s, it is argued that the optical regime of the classroom underwent a decisive change during the second half of the nineteenth century, when monitorial teaching was superseded by teacher-led whole-class teaching. This new method of teaching implied a new kind of surveillance in which the teacher was expected to remain at his/her desk in order to see the class. The meaning of this optical regime is discussed in relation to Foucault's concept of the panopticon and Mathiesen's concept of the synopticon. While both concepts highlight important aspects, it is argued that they do not fully capture the essence of specific features of surveillance in the history of the classroom.