I teach high school theatre.  Even with a cast of 35, it can be daunting.  We only have 3 more students than last year, but it seemed a lot worse than just 3 more bodies.

Instead of shushing that gets ignored or even "blowing up" at them, I now have rule.  If you can't keep your mouth shut when it needs to, the entire company runs a lap around the rehearsal hall or, if we are in the theatre, they run stairs.  They dread my "run a lap" or do 4 flights, but usually after the first lap or set of stairs, they stay shut up.  The few times there's been a problem during performance, I send them around the building or make them do push ups.