My name is Martin and i’m 12 years old. I think it was a bit of an overreaction by the teachers. You should be allowed to do whatever you want with you own body, as long as it doesn’t hurt anyone. I don’t know if everybody should go to school with dyed hair but maybe it is a good idea after all, to make the teachers understand that you should be allowed to dye your hair. If it doesn’t work you should talk to someone else, like your parents. So that they can talk to the teachers. Good luck!