This being Ithaca, there are probably many families who would want their children to see the play in question. But of course many parents will not, and they are placed in the uncomfortable position of having to send a special note to the school and having their kids removed from the classroom - something few parents or children enjoy.
This story illustrates why I believe the only real solution is vouchers. If you want to send your children to this kind of school, fine. But give others the option to send their kids to schools where other values are taught.