3)On punishment: Leave it up to the co-teacher. Taking the discipline into your own hands only backfires. The kids won't listen to you and the co-teacher will feel out of place. If they won't be quite or listen, simply refuse to speak until they do. Request their silence and when they don't listen just tell them you're waiting. Sometimes I'll even pull a chair to the front of class and sit down. It surprises them and its also a wake-up to the co-teacher that he/she should be doing their job.