Actually no you didn't, unless your answer is that anyone can get up and say anything they please.
Is that your answer?
The valedictorian or any other scheduled speaker can say whatever they want. Government censorship is far more dangerous than anything a kid can say from the stage.
There is no right to go through life without ever hearing something you find offensive. The idea that there is such a right is why school bureaucrats prohibit speeches that thank God. From your posts it appears that you also agree with that censorship by government bureaucrats. Is that your position?