How can we improve education? Fryer et. al., study the effect of cash incentives to teachers. This has been studies before, but the authors explore a variation: two ways to provide cash incentives: 1) paying teachers based on students' performance when the final exams are completed, versus 2), paying teachers at the beginning and asking money back if students do not perform as expected. The authors find that the second method works better to improve students' performance.
The paper is here.