At first glance, even second glance, this seems like a terrible idea. Motives to learn should be pure and intrinsic. And if learning for the sake of learning doesn't click, the correlation between education and income ought to be sufficient motivation. Won't paying for grades inevitably lead to kids demanding money for, say, taking out the garbage?

At the moment, only a handful of places are trying cash-for- performance. The largest experiment, involving 70 schools in New York City's poorest neighborhoods, starts next month. Fourth- graders who score perfectly on state exams will get $25; lower scores earn less. The cash rewards double for seventh-graders.

In neighborhoods where students can get rolled for lunch money, it's important to try to ensure that the rewards stay safely with those who are earning them. New York and Tucson school officials have lined up banks willing to place direct deposits into accounts for the students. Bank officials will visit the schools to teach financial literacy.