Engagement and actual occupation. This is a strategy which is particularly helpful with large classes.
Take, for example , a mentally engaging activity like the one just described where the children are trying to guess which picture or word one of their classmates has chosen. This will keep even a large class happy for a while because it is fun and it makes them think. Even so , there are two disadvantages. First , any single child in the class is not likely to have more than one or possibly two opportunities to speak. Secondly , only one child is speaking at any given time. However , once you have established how the guessing works you can then change the activity into simultaneous pairwork for the whole class , adding actual occupation to the mental engagement of the original idea.