The promise of a big bonus might seem like an obvious way to make employees improve their work, but there’s still a lot of debate over whether that strategy works with teachers.  A new study out today shows that it can, under certain conditions.

In Washington, D.C., $25,000 is half of what some public school teachers make in a year. The most effective ones can earn that much as a bonus.  

The controversial IMPACT system can make teachers better, according to researchers at the University of Virginia and Stanford.

“Teachers have to know what they can do to earn those incentives and they have to believe that it’s within their control to meet the expectations,” says Stanford Education Professor Thomas Dee, a co-author of the study.

The least effective teachers can lose their jobs, and too soon, say some critics. Others argue that teachers’ salaries should be tied to their education and experience, not students’ test scores. 

The D.C. system also factors in teachers’ classroom performance and collaboration, so it’s “game-changer” according to Kate Walsh, president of the National Council on Teacher Quality. “D.C. has put all the right ingredients into the pot and they backed it up with serious money,” Walsh says.

But results may vary; the study warns D.C.’s system “is not one size fits all.”