Where can I submit a short story?

I'm in 8th grade and I have a short story that advanced me last year when I took the State Writing Test. I really want to submit it somewhere. Like, to a magizines with childrens short stories or into a contest. My dream is to be some sort of writer when I get older. Can you please give me some sites I can go to to acomplish these goals of mine? =) Thanks!