Hi, 40yr old here and I remember going through what you have gone through. Stay strong. Hard to tell you to ignore the people who are laughing at you, but you should ignore them. Seek help from your teachers and maybe your school if they have speech therapists. Study hard and focus on what you are good at. Also focus on what makes you happy. Also try to find stuttering support groups like a local NSA chapter. You are young with many many years left to grow and mature and become a contributing member of society. There will be good days and bad days for you. Find a good support base. Wishing you the best.