I'm of the opinion that pretending is not going to make it the real thing just because a person decides to slap on surgically, a penis, vagina, or some boobs on their body. Hermaphrodites are different story for which it's clearly a natural third sex in my opinion for which two pronouns would apply, should the parents decide one sex or another then one desire pronoun would be sufficient.
I never said that a person who is transgender however should be completely disregarded with their wishes. But I also feel that if a person does not want to address another person when it comes to pronouns, that person should retain that right to just stay silent on the issue and not say anything about it at all. If the teacher was just being an ******* to the student, and press the issue, then I can see disciplinary measures.
For a society and or Institution to force a person to say one thing or another under some kind of idiotic threat of not being PC enough , that Society can **** off with hopefully a stern reminder that such a society or business still has a lot of growing up still to do.