The fact that you were willing to present to a whole class and not just completely avoid it should be an achievement in itself that you went for it and to me, even though you stuttered, I think your teachers still interpreted the message you were trying to convey. Most teachers are decent and even I've stuttered a lot giving the name of my town I'm from when I was in my first year of uni but the teacher didn't question if I stutter and she still understood what I was saying! :) Even non-stutterers feel so worried on giving a talk. I'm sure if it was you then you would feel proud of someone still managing to deliver a talk. I feel as though because there were lots of people there then you may have felt very under pressure of needing to be a fluent speaker. Try looking into Megan Washington for inspiration, she did a TedTalk on her stutter and still nailed every word of it. I would recommend looking into speech therapy if you haven't as you don't deserve to be experiencing severe confidence issues to let your stutter define and win over you on one setback.