I don't think children should have to work to put food in their bellies or to keep a roof over their head. But I do think children should work along side their parents when possible.
My husband works outside the home, and I have always pretty much always ran some type of home based business, while property managing (though I retired from the property management and sold my rentals) My kids has always worked beside us when we have had work. They know how to do basic maintenance, and even when they were small they could still paint the bottom part of the walls.
I believe in teaching children work ethic while young, and allowing them to earn money for that work. But also allowing them the freedom to take more breaks and to go play.