I was in your shoes and I'm not going to tell you that it gets better but what I can tell you is to search online for speech therapy or teen stutter support groups. I had a severe stutter from grade 1 to college. Speech therapy helped me along with hypnosis. Reach out and seek help. It's pure ignorance on the part of your teachers so I would contact the ADA (Americans with Disabilities Act) and have them educate your school. Just know that you are not alone in this.