hmmmm, I have mixed feelings, a believe in freedom of speech, however, the school has rules and she did not follow them.........
the question is, of course, are those rules consistent with free speech. The fact that they said no in advance doesn't let them off the hook. Free Speech has been the battle cry in the culture wars, and it will continue to be til we sort this stuff out.
From what I understand, she spent months making the dress, and a teacher overheard her talking about it the day or two before and she got a phone call that night telling her not to wear it.
In that circumstance, I think I might have the same attitude.