"This guy's not wierd, he's delusional. He doesn't need a doctor hacking at his body parts, he needs a shrink.
"
Nah, he's just wierd. He teaches math. Need I say more?
Seriously, it's not going to be that big a deal, in the long term. The school can't fire him, legally, because he's not really doing anything illegal.
He's going to teach math to kids. They probably have teachers who are a lot more wierd that this guy.
It's just not worth the stress. I know what my father would have said, back in the early 1960s when I was in high school. He would have said, "OK, the guys strange as a three-dollar bill, but if I hear about you saying anything about him or harassing him, you're going to be sorry."
Should parents be able to remove their kids from his class? Sure, as long as it is feasible. In many cases, there's only one teacher for some math classes, so it may not be feasible.
After this school year, nobody will care.
It will be a big deal to him. He needed help and he got mutilated.
In the movie "Batman Begins" Bruce Wayne said, "Anyone who goes around dressed as a bat clearly has issues." Batman has issues and he's dangerous, but only to criminals. And, if he decides to, he can put his batsuit away.
Someone who actually has a doctor take a knife to his body because of his issues - well, do we really know what else is going on inside his head?
An effeminate man who doesn't try to pretend he's a woman, I'd agree with your dad. This guy is much more than that.
Shalom.