Sex change according to Judaism

I can't say what the 'Judaism position' is, because there is no such thing. There are different opinions. You can see my opinion here: https://mikyab.net/%D7%A9%D7%95%D7%AA/%D7%9C%D7%94%D7%98%D7%91%D7%99%D7%95%D7%AA-%D7%95%D7%90%D7%9E%D7%95%D7%A0%D7%94/ The question of how you should treat him is a different question. The decision is theirs, not yours. The question may arise as to what to do if they decide to do so. How to treat him after the surgery. I don't think you should give him normal treatment, but students will certainly have questions and you shouldn't cover up for him if you think it's forbidden. You can explain to the students that you think it's forbidden and also explain the distress that caused this decision, but tell them that it's the decision they made and you recommend that they treat him/her in a humane manner despite the differences of opinion.