I think with any taxpayer funded institution, first amendment protocol (
Lemon v Kurtzman(403 US 602)) should be followed.
Error on the side of more freedom and not less, and any restrictions need to pass "
The Lemon Test".
Can a person provide a reason that's both A) compelling -- meaning it needs to be something of substance and can't purely be "because I just don't like it", and B) needs to be secular and not a case of the government enforcing a rule that's clearly catering to a religious belief.?
If a person can't provide a reason to ban it that fits both of those criteria (which is going to be very tough since we're not even talking about a compulsory activity -- nobody is forcing anyone's kids to partake in his), then it shouldn't be restricted.