I'd say a grocery store, but then again that's just where I work. We hire at 15, I think, but you can get a work permit if you are 14. However, be careful, because the customers at a grocery store are almost always pissed off for whatever reason. I had this one woman that made me go fetch her another package of biscuits so she could use a coupon, while there was a line of 5-6 customers behind her. She also had me go check two prices, and gave me some sort of smug "Mmmhmm" when I said that she was technically right, due to an incorrect/outdated sign.
But.. I digress. I didn't get a job until I was a junior. I think that's about the time that everyone starts getting jobs. For now you might want to stick to mowing lawns, babysitting, and tutoring.