I just heard about a cool idea a local 4th grade teacher is using to teach kids a lesson most folks don't learn until after college.
Here are the rules:
Each week, you get a salary of funny money (I think it can vary depending on grades and behavior, but the details aren't important). There are cheap, flashy toys you can buy with your funny money.
Catch number one: You must pay rent on your desk. The rent turns out to be a significant amount of the funny money.
Catch number two: You can save up and buy your desk. This takes several weeks of saving. After you've bought your desk, you no longer pay rent, so you've got more money each week.
Catch number three (my favorite): After you've bought your desk, you can buy another student's desk. They must pay you rent (unless they save up and buy the desk).
What's funny is that the same thing happens every year - the boys blow all their money on the flashy toys, while the girls all save up and buy their desks. Then the girls buy the boys' desks. Then the girls buy all the best goodies. The boys get outraged at having to pay rent to a girl, and that the girls have all the money.