Fine. Let them bring suit.
If a group of Christians finds the teaching of their holy book as a thing of beauty offensive, they can take the school district to court to have it banned. Everyone who has objected to having Christianity forced upon them in non-elective activities has had to go that route.
That would have an interesting effect on the whole "religion in school" argument. If the Christians have teaching the Bible banned, they certainly can't say they're being oppressed.