After a couple of minutes, the exchanges were brought to a close. A great deal had been achieved. Some pupils knew more than they has before. Some pupils has become teaching experts and had rehearsed their own understanding of the lesson ideas. But even more to the point, the whole class has participated in joint learning. The learning was a shared activity. A passing Deputy Head may have suspected a riot, but this was expert teaching. Adolescent energy was deployed by the simple structure of Got, Not Got and the unquestioned underlying assumption that learning had to be done.