From source: TwilightLexicon
This is one of those things that you shake your head at in disbelief. Even more bizarre it’s a public school that has to adhere to state law, and we’re pretty sure denying a diploma when you have completed course work is illegal. You can deny privileges: prom, field trips, etc, but not the diploma if you have actually completed all the work. By virtue of the fact she was the valedictorian, and in fact was delivering the speech at graduation, it would seem that she had. They only way there might be a loophole here is if she signed some kind of contract where she acknowledged losing her diploma if she went off script. It makes you wonder,if these folks have acquainted themselves their own US History and civics classes. The first amendment, which given this is a public and not a private high school would apply here, you can say any number of things that are unflattering, but they can’t withhold a diploma for that if you have in fact completed your course work.