Depends on the kid. Do they treat workers disrespectfully, or not understand that money shouldn't be recklessly spent? Absolutely have them work fast food for a night -- so long as an adult is there to make sure there's no safety issues and they're paid full minimum wage for it, I'm all for it.
I had a chemistry teacher in high school who maintained that everyone should have to work retail or fast food once, and as I've grown older I completely understand what they meant. Some people are naturally not dicks. They don't look down on workers at Walmart or McDonald's. For others, it's a lesson they have to learn. They need to work in that position to understand what it's like.
That doesn't mean we should draft all kindergarteners into the work force. But the occasional experience to show them what a minimum wage job is like? Absolutely. If we want kids to grow up voting for minimum wage increases and universal labor rights, they have to learn these things somehow.