Three things I have learned during my time teaching 10-12 year old children:
This age group can concentrate for longer periods of time than younger learners and they are able to do more various activities, longer tasks, tasks that require more concentration and thinking.
They don’t consider themselves children (although they are still children). They still need to have fun, to enjoy learning. I find it very difficult to choose the right activities for this kind of learners. Too complex activities will fail and too simple activities will be considered babyish (different kinds of puzzle activities work the best for them). Giving them some control in the lesson creates a game atmosphere and captures their attention (for example ask a student to choose the next speaker).
They find interesting materials and activities that are related to other subjects they are studying such as geography and history. A contest game is the way to go with this age group. They love competition (especially boys vs. girls) and this kind of activity works the best with a noisy class.
10-12 year old learners take learning more seriously and they can work in pairs/groups very well. Besides the opportunities to enjoy learning in a funny way, the teacher can establish rules and routines.
They love talking about themselves, their friends, their families, their homes, travel, and school. For some reasons they find these topics easier than others and they are able to use new vocabulary in this context.