Our school doesn't have one that I know of, but my daughter's classroom does! The teacher calls it CLASSROOM CASH. The teacher uses things like completing homework assignments daily, doing exceptional listening, etc to earn $1. Things like not being nice, not listening, etc. means they have to pay it back.
At the end of each week, the kids that have CLASSROOM CASH to spend get to shop at the teacher's STORE. She mostly has dollar store items and some bigger items like Zhu Zhu pets and whatnot. It costs about $2 classroom dollars to buy ONE little item (prob worth about 50 cents).
Typically kids earn $1 a day, maybe more for exceptional behavior.
However when they lose money it can be $1 or even $5.
The kids who don't do homework or have behavioral problems in class, never seem to have any money to spend. The good kids do well, and even save up money for days or weeks to get bigger toys.