Lol. I haven't seen choir rules enforced in a while. I've played at a few places where you don't sing if miss rehearsal without a good excuse. There was a point in my church if you missed Sunday morning prayer with the choir you did not sing. Also no walking up at the last minute once church started on Sunday.
If I was an mom I would make a few guidelines for the music like:
Two rehearsals to prepare for new songs. If you miss both rehearsals no singing that Sunday. This would be adjusted based on progress.
I would prepare at least 3-5 new songs every rehearsal based on how many songs are sung on Sundays.
Musicians will have music at least two weeks in advance.
Some sort of dress code for directors with backs facing congregation. Nothing worse than someone in tight pants or dress. You get the idea.