In my experience, my stuttering gets worse the more nervous I am. The more I think about my inability to speak naturally are also the times when I experience it the most. It's possible you are having a similar issue. I know it's hard but try your best to not feel ashamed of stuttering. Generally there is very little you can do about it without talking to people. Not to mention, anyone who is making fun of you is not worth your time at all. I personally never told my classmates as I thought it was already obvious enough. It's really up to you though. I don't think either way is better then the other. If you do get a particular bad stutter, I've had decent success by just laughing it off by saying "I sure wish I could talk without stuttering" or something of that nature. The worst thing you can do is not talk at all. I did that for most of my life and I still regret it to this day. I hope it goes well for you!