One of the basic tools for teaching economics in the lower grades is a token economy. Students are "paid" with classroom currency (often designed by the students) for completion of tasks, jobs in the classroom, even grades. The money is then available for them to use in various ways - free time, library visits. Some teachers even make it a necessary part for participation in enhancement programs. One teacher told me that if his students wanted to take part in a stock market simulation he ran each year, the students had to buy in by saving a certain number of classroom dollars.
Token economies are sometimes also used as a classroom management tool. Here's an interesting post on one such experiment. (HT to Arnold Kling at EconLog.) I encourage you to read the comments, as well. And share your thoughts with the rest of us.