Ugh... I could have sworn I just responded to this, but it's not showing up, so I'll try to remember what I wrote:

I'm so sorry all that happened.
Did the teachers give you any explanation has to why they won't let you wear it?
I have personally never heard of teachers not letting kids wear jewelry at school.
Have you thought about talking to a school counselor and explain your situation
and see if they can help you convince the teachers to let you wear it?