The school or district would certainly have grounds for a suit if they wished to pursue it.   

The point I was making is that in a stadium with hundreds or thousands of people looking across a field at each other and many if not all of them having cameras something like that which was described WOULD have been captured on tape.   Just like a streaker would have been caught on tape by someone.    That NO ONE of hundreds or thousands of fans was offended and took a picture suggests very very strongly that no such thing happened.  Moreover if it did happen and still no one has a picture or video or remembers seeing it that would argue it was so poorly displayed no one could see it and be offended by it.   

Either way no letter should have been sent.