Its much easier as you get older. When you're in high school, you're really self-conscious to the point of hypersensitivity. Getting up in front of all these people that you know and live next to and will see everyday for a couple more years, its nerve rattling. There's the whole obsessive image thing in high school where your own worrying about screwing up will cause you to screw-up more than you otherwise would. Blah.
When you're in college, or older, its like, "Hey, I don't know any of these people, or I only know a few of them, and I really don't care what any of them think!" That helps.