From the New York Times:

“…The initiative’s success is refueling a debate over whether cash bonuses can coax improved performance from teachers and students – a New York City incentive program was disbanded – and whether paying students for schoolwork diminishes their ability to feel intrinsic pleasure in achievement for its own sake.”
 
“Roland G. Fryer, a Harvard economist who won a MacArthur Foundation award last month for his research on educational incentives, said that cash alone did not consistently raise achievement, but that combining payments with tutoring, teacher training and other tactics could be promising…”