I felt exactly like you when I was at school, i am 20 yo now and study in med university, it's just a really hard phase of life, school is a hell place, you just need to get through this, and stutter will become better, you just need to not overthink it and not be afraid that you will stutter (this is very important), all my classmates know I stutter, but they still like to talk to me, it's about being positive, sure, this is very very hard, but it's possible, you will get rid of anxiety and won't be afraid to stutter one day, believe me, just you need time, you got this mate