When I went to summer camp (here in the great state o' Georgia), I remember that some of the youngest counselors and assistants were 16 and 17. They lived at camp during the week, and sometimes went home on the weekends. Most of the counselors were college students, but there were always a few younger ones every year. This was back in the early '90s, so it's possible that things have changed a bit since then.
I got my first job at age 15. I answered phones at the engineering firm where my mom worked. I wish I'd done the camp counselor thing at some point; 15 was way too young to start acquiring a "business casual" wardrobe.