This paper reports on a study of classroom interaction as a multi-party and multi-activity phenomenon. On the basis of video-recorded lessons in secondary education schools in the Netherlands, observational records were made of the behaviour of individual students throughout lessons. The main argument in this paper is that when students engage in parallel activities, and in spite of their very different ways of doing this, they show an orientation to the activity in which the teacher is involved as the central activity. It is argued that one aspect of what makes a lesson recognisable as a lesson is this common orientation to the teacher's activity as the central activity.