I'm not sure if your school would allow it, so you'll need to ask your principal but when I was in high school, I raised money by selling candy. I bought the candy in bulk (like Sam's Club or Costco), then charged like 25-50 cents each. (which was just over double what I had paid) I had another classmate who did the same thing, only he sold roses.
There are lots of cool things at the Oriental Trading Co that you could buy & resell too. (bookmarks, coinpurses, stuffed animals, toys)
Good luck!
