Good reasons for seemingly bad performance

The evaluation of students’ competences in educational institutions tends to be associated with the degree of the students’ mastery vis-à-vis specific, preordained curricular goals. Aside from such sanctified measurements of achievement, however, the analysis of competences is in fact embedded in everyday classroom interaction; or rather, it constitutes a critical element for organizing instructional activities. Taking a 8th grade math class as an example, the present chapter examines how two students’ competences are made publically available during their presentation of a geometry proof delivered at the blackboard, an activity situated in a lesson. Through a multimodal analysis of a series of episodes at the board, this chapter demonstrates how the geometry lesson is achieved through the participants’ concerted activities.