The official lesson and the lesson about who gets interrupted happen at the same time.

Two lessons run at once. There is the subject, and there is the ongoing demonstration of whose voice carries, who gets interrupted, whose question is treated as a contribution and whose as a delay. Children learn the second one thoroughly, and it is never on the syllabus.

In any room you run, track who gets cut off and who gets finished. The pattern is usually visible in a single session. Fixing it is mostly a matter of noticing and then deliberately returning the floor to whoever lost it.