You're in high school, I imagine that means some of your classmates would not be opposed to violence (a sad truth in the America school system, at least). So if you suspect that would be the case, then don't take my advice. But if you don't think they'd resort to violence, feel free to call them out. By the time you've reached high school, you're either starting to mature or you're stuck in an immature phase and are unlikely to grow out of it. The person that laughed at you is immature. You don't have to cater to them, and you don't have to be scared of them. Telling the truth is always an option and never let anyone tell you differently. There's a huge difference between just saying who it was, and responding truthfully when the teacher asks you who it was. One is tattling, one is not, I'm sure you can tell which is which. That being said, I didn't develop a stutter until long after high school, but what might help you in the meantime is to write down what you play to say before you say it. I used to do this and it helped me immensely with my stuttering. Eventually I learned how to simply rehearse what I wanted to say in my head shortly before I said it. I sometimes take a bit to answer questions now, and very rarely I will get someone looking at me like I'm an idiot, but I'm always able to respond in a reasonable amount of time. Sometimes the stutter comes, sometimes it doesn't. If it does, I take a beat, take a breath, center myself, and am able to continue.