I can fully relate. When I was at school and university I was always underperformed because of stuttering. The most disgusting is the fact teachers, who were aware of my problem, still were decreasing my marks. I can advise you to not to leave these situations like this: be brave and go to complain about that all such cases. Dont let people make you feel like you are worse than anyone else. Be more bitchy, people will never change unless you will defend your boundaries. Good luck and I believe in you!