I took a speech class at the university that I'm currently attended because it's required for my major. Otherwise I probably would've avoided taking it. Anyway, the class won't laugh at you when you're making a speech unless you added something to your speech like a joke or something where the intended effect is to make the class sort of laugh. What I find though is that most people aren't even paying attention to the speech your giving since they probably just want to get out of that boring class as soon as possible or they just simply tune out. Heck, after I gave my speech, I almost fell asleep because some of the topics or the way the person delivered the speech was sort of boring. It's a generalization I hate to make, but people in high school are generally immature compared to those in the university. I did notice that when I made a speech in high school and I totally froze because I was very nervous and on the verge of having a breakdown I saw some of my classmates snickering and laughing. I was so embarrased for a while, but I don't really let it affect me anymore now that I took back on it.
Giving a couple of speeches in the same class is good though since you become familiar with the faces and even though you might not know them in a personal way, it's a lot more comforable giving speeches to familiar faces. It was nerve-racking the first minute or so I was up there giving the speech, but once I was on a roll it was sort of easy for me to say the rest of the speech. Of course it also helps that you practice your speech ahead of time and that you have a very nice professor (I lucked out there). Taking a benzo and beta-blocker also helped me get through the class so I didn't get a breakdown or totally blank out when I was in front of the class because of total fear.