Hey I know you're feeling like shit. And it's a terrible feeling because you couldn't have done anything to really prevent this from happening. Despite that I will say that how your classmates and your partner acted is so rude and inconsiderate. You stutter. It's just a tiny part of what makes you YOU, so it's really not the end all be all of what people think of you. Did you practice the presentation with your partner beforehand? I have found practice to be super helpful for big presentations.