Here is a a link. She DID break the rules, and she was well aware of that. It says ZERO tolerance policy.
HS valedictorian denied diploma after saying word
There is zero tolerance and then there is zero tolerance. A high school in Oklahoma with a
strict zero tolerance policy against profanity may have overreacted a tad in refusing to grant a diploma to a graduating senior (and not just any graduating senior but the class valedictorian) because she said H-E-double hockey sticks in her graduation speech. The teen, Kaitlin Nootbaar, was on NBC's Today Show on Wednesday, where she told host Matt Laurer that she has no intention of apologizing for her offensive choice of language. “I know what I've achieved,” she said during the interview (video here), “and the fact that I don't want to give an apology, maybe I'll never get my diploma and that's fine.”