Your post: "The school has a state charter and the foundation by law has its bylaws."
But where is this mandate that requires discrimination on the basis of the renter's beliefs and opinions? Basically when it comes to public facilities being rented out it's rent to all or rent to none.
I can rent a publicly funded library room or tax supported school auditorium when not in use if others, Hare Krishna's, Darwin doubters and believers, Prayer clubs, or whatever are allowed to and I don't have to meet an ideological test.
If I'm not allowed then no one is allowed.