The aim of this article is to further the understanding of how content is learned in classrooms, using conversation analysis (CA) and variation theory for the analysis. Classroom video materials from two mathematics classrooms in Sweden and the USA are analysed. A result of the study is the empirical explication of the tension between the need for teacher content control and the simultaneous contradictory need for student participation in educational interaction. The article also develops variation theory toward a more sensitive understanding of the sequential implications of interaction and suggests CA can benefit from more systematic understandings of content orientation in interaction. In doing so, the presumed gulf between acquisitionist and participation understandings of learning is challenged. (Contains 2 figures and 7 notes.)