For most of my school days, I was very shy and reserved, often preferring to remain obscured and overlooked in class than to ever have to actually talk to these people. I would sweat, clam up, and struggle to talk without stuttering (I had a bad stutter from ages 10 to 12).
A very excellent teacher for my creative writing class (there were 8 of us in the class) taught me a fantastic trick to get over my stage fright. Since we had to read our work aloud, and he saw the difficulty I was having, after class he gave me a big hint. When standing up there, do not make eye contact with the people in the class. Pick 3 points in the distance, just over the student's heads. One point in front, one to the right, and another to the left. During your speech or reading, look and lock your eyes on these points. Every 5-10 seconds, switch to another point to look at.
What this does is gives the audience the illusion that you are making eye contact with them, scanning the audience as well. But in actuallity, you are avoiding contact, and at the distance you are from them, they cannot see that fact. Over time, and with repeated readings and speeches, he said, you will grow more confident, and less unsure, therefore you will begin to make eye contact and warm up to your audience, and won't need the "crutch" of not looking any more.
Remember, talk loud and sure. Speak from your gut and project your voice.
Good luck, public speaking is one of those tools and traits that is most required as you get older and enter the business world. Never be ashamed or embarrassed of anything you have to say.
My 2 cents.