I did this several times before. It worked out fine. The subs (there are two directors, so two subs) just wandered around and checked on the kids to make sure they were on task. In fact, we split the group by sections and still made it work. I'm doing something different this year (my post below) because we haven't had time to do "pass off" with bad weather days, surprise benchmark testing days, etc. We are using TMEA as a time to get caught up on this. Sometimes you just need to trust the kids to work on their own. If you've laid do the expectations from the start and trained them on what to listen for it will work. And I do this with middle school kids (just not beginners. They aren't ready for that and the classes are WAY to big).