I remember that LA County (California) gave school students a pamphlet that had the conditions for minors to get a job in that jurisdiction. 16-year-olds could definitely get jobs after going through a few hoops. 14-year-olds had more hoops, including that it had to be a family business, such as Junior filling in at Father's jewelry store after school. I think it was possible for a supervised 12-year-old to legally work for a wage lower than minimum, but again it had to be a family business.

Ohio is similar; family businesses and farm work have special exemptions, but otherwise 16 is the norm.