Tops and Bottoms, by Janet Stevens, is the story of a crafty rabbit outwitting a lazy dumb bear. The bear allows the rabbit to grow crops on the condition that he gets to keep the tops of what the rabbit produces. Naturally, the rabbit grows root crops and leaves the bear with nothing. The bear wise to the rabbit's ways changes the rules, insisting that this time the bear gets to keep the bottoms (roots). The rabbit then grows corn, leaving the bear again with nothing.
The economics your kids learn:
The behavioral response to taxation