You shouldn't mock students in general. All it does is make them uncomfortable, sad, and/or angry.
When I had braces, I had to get an awful device in my mouth. It was called a tongue crib. It was too big, so it dug into my tongue. It gave me a lisp, and I had little divots in my tongue for a while.
A couple of teachers at my high school made fun of me for my new lisp. One of those incidents was on a school trip where I was in a van with a bunch of teenage boys.
Every incident was humiliating. I went to my orthodontist and told him what was up. He got me a smaller tongue crib that I only had to wear at night.
Still had a slight hint of a lisp for a few years. And if we're being honest, it still kind of sounds to me like I have it a little bit.
Putting students on the spot and making fun of them is not cool. School is supposed to be a place of mentorship, not bullying. That's what the other kids are for!