I started and now run a small school store at our elementary (3rd - 5th). Since our school is already using every square inch, my husband made a rolling counter display. It folds closed, and has plexiglass fronts. I roll it into a closet to store it during the week. Since it is small, I don't have much storage room and tend to order stuff almost every week. It makes its own money, and enough profit to fund things like Family Movie Night.
We are open on Fridays from 11 to 1, when there is a lot of traffic in the foyer from kids coming back from lunch. They can only buy on the way back so they don't spend their lunch money. I have a few 5th graders who help me during their lunch and recess.
We have items starting at 2 for 25 cents (the small pencil sharpeners) up to 2 dollars for the spy pens, which I only have occasionally. Most of our items are 50 cents to 95 cents. I always have different sharpeners, erasers, and mechanical pencils. The other stuff comes and goes - bracelets, wallets, scented highlighters, bookmarks, keychains, and memo pads. I buy some stuff at Big Lots, the office supply store clearance area, and even WalMart. Right now, since its October, I'm selling some halloween stuff - pencils, glow-in-the-dark bugs and bats.
We just started selling popcorn on Fridays also, from 12:30 until the end of the day. I was buying it from a popper in town and rebagging it, but we made enough money to buy our own popper.
I would be more than happy to tell you more!