On my audition form, which both students and parents sign, it states
The rehearsals will get longer and more intense the closer we get to the show. Please plan accordingly!
Every actor is expected to be at each rehearsal for which he/she is scheduled. Unexcused absences may count against an actor and if an actor is frequently absent without permission, they may be dismissed from the show."
"I understand that, if cast, I am expected to be at all rehearsals and performances. I understand that failure to attend scheduled rehearsals without permission for an absence may result in disciplinary action, including being dismissed from my role."
Our rehearsals begin right after school and go until 5 most nights, 6 or 6:30 for musicals as they take more time. Once I have a cast, I get them a rehearsal schedule that works around conflicts as best I can. I only call the kids in that scene for rehearsal, whereas my predecessor called everyone everyday and if they weren't rehearsing they were to sit in the auditorium and watch the others. I can't manage that many kids doing nothing, so I prefer they just not be there and use that time to stay caught up on school work and household things instead.
I insist that the kids take enough rehearsal schedules for themselves and the households they live in. I encourage them to highlight the days/times they're rehearsing instead of just handing their parents the schedule so it's easier for the parent/guardian to find the days their kid is rehearsing. I also keep a facebook group for each show and the parents and students involved are added to it. Rehearsal schedules are uploaded to the facebook groups as well. I am very strict about keeping to my rehearsal schedule and if I hold the kids late it's no more than 15 minutes and no more than 2x per show. It's really important to me that everyone learn that the schedule is the schedule, period.