You shouldn't be ashamed. Out of everyone else in your class, people are going to remember you because you stutter. No one else in your school can say that about themselves -- that they are able to make an impression every time they open their mouth. You can use this fact for better or for worse. For me, it gave me an excuse to be a charismatic smartass because fuck it -- everything I said was going to be fucked up anyway, so why not say whatever I want. You'll also get a girlfriend. Having a stutter forces you to be a good listener and develop more empathy towards people. Chicks who are worth being with love that. Trust me, it does get better (I'm 29). In the end, high school doesn't matter, and if you develop a cavalier fuck it attitude towards your stutter, it will help you the rest of your life. What's the worst that can happen if you stammer through a presentation? Will the earth open up and swallow you whole?