Thanks EmmyLou.
I certainly don't encourage the other children to bully or 'grass up' the talkers. If it happens too often I just open the backstage door so that I can spot the culprits, but they need to learn to do it for themselves.
But the talkers do feel ashamed when the other children are exasperated that their rehearsal is interupted. They're all there because they love their drama, and all of them want to work really. It's just that some of them (when with their peer-group) are congenitally incapable of keeping quiet for more than two minutes.
I'm in quite a priveleged position, as I teach one small group at a time, and I supervise their break-time. No bullying here, ta.
Greensleeves, you may not agree with my methods, but I am emphatically not a lazy teacher. I'm a bloody good one as it goes, and I also happen to like and respect children. Unfortunately not something one can say of all teachers.