What are the GED requirements?

I'm 18 years old and I'm currently a sophomore in High School.

A little back ground:

When I was a freshman (two years ago) I got very sick and missed 3 months of school. During that time all of my participation classes went down the drain. I also failed out of science and math because they weren't my strong subjects and not being in class ended in me failing.

So then I repeated my freshman year last year, but I also had sophomore English and history because I passed those from home during my first run through freshman year. I got to the point last year where I really hated myself for failing and I've always been the nice girl who everybody felt the urge to pick on so that began to get me down as well.

This year rolls around and I'm supposed to be a Junior but i'm a sophomore and I'm about to turn 19. If I continue on and do this year, and then the next two years I'll turn 21 a month after I graduate. To me, this is unacceptable and I need to do something about it.

I've opted to drop out and get right into taking my GED because I know I'm smart enough to do so. I've already got a job as a waitress at Pizza Hut and I understand that's not a good job, but I do make fairly good money especially in tips. I've talked to my employer and he has said that as long as I get right into my GED i'll be able to continue working. With this being said, I heard from a teacher that in order to get my GED I have to wait till my original class would graduate and then I can get it. I don't want to wait another year and be a bum. I'm wondering, do I have to wait to take the test? Can I take it a month or two from now after I do some tutoring in my sore areas? I'm confused at that, and also a little discouraged.

Also, if you've got any personal experience as a drop out I'd appreciate hearing about it. If you're going to tell me I'm an idiot and need to stay in school then I'd really appreciate you not answering at all.