I grew up in cotton country and every fall schools let out for two weeks for cotton harvest. They made up this time by starting a week earlier and letting out a week later. Every kid between about 8 years old and high school seniors picked cotton. The cotton got harvested and kids made some money, many bought their own school clothes with this money.
Of course that was in the 50s and early 60s.
I think about this and laugh - how impossible this would be now, especially here in NY. The insurance lawyers and public unions would be all over such an idea. Many parents would scream, but if given the choice, many parents would also like the idea. Earning honest money is one of the best things you can teach a youngster.