Same thing happened to me with a Philosophy teacher in 10th grade. You would think she would be understanding because of her subject, but no. She just brushed me off, when I tried to swap the presentation assignment with something else because of my stutter. Anyway, take any victories you made in stride(with presentations and public speaking). You now know that you can deliver excellent presentations, which means that you can do so again and again. Keep practising your speech and keep trying. Much love from Bulgaria.