Keep the big picture in mind. Think of how many more opportunities you'll have once you graduate! Don't think too much about the day to day, just focus on the end goal of getting a diploma.
A little embarrassment for a short amount of time is totally worth it in the end. Besides, you shouldn't be embarrassed, even though I know it's got to be an awkward situation. Don't let the other kids get to you. This isn't about them, this is about YOU. And you achieving a goal, doing it for you. I've seen elderly people go back to high school and college! Just have a "So what" attitude towards anyone who makes fun... all it does is show their immaturity if they do make jokes. Best of luck!