Chicago Public Schools is offering its principals bonuses—as much as $20,000—for exceptional improvement in student test scores.

Merit pay is a hot topic in education right now. WBEZ checked in with one of the country’s foremost researchers on the issue to put Chicago’s new principal bonus program into context.

Let’s get one thing out of the way: Matthew Springer doesn’t have an opinion one way or the other on merit pay for teachers or principals.

SPRINGER: We’re 100 percent agnostic on the issue—we’re hoping to provide better research and evidence to determine whether incentive pay and different forms of merit pay are an effective school reform strategy.

Springer directs the National Center on Performance Incentives at Vanderbilt University.

While he’s agnostic about merit pay, he’s absolutely convinced of this:

SPRINGER: That the current way in which we compensate teachers—and I include administrators in that—is ineffective.

Springer’s thinking goes like this: Teachers are vital to education. Some are good at their jobs, some aren’t. But we don’t pay them according to how good they are. We pay them according to years on the job and the degrees they’ve earned.

Merit pay programs attempt to change that.

Mayor Rahm Emanuel said yesterday he wants the carrot of a $5,000, $10,000, or $20,000 bonus to drive student achievement.

Springer has looked at that kind of thing in New York, Texas, and Nashville. Here’s the bottom line:

SPRINGER: There have only been a handful of studies investigating the impact of a teacher or administrator incentive program on student performance, and in general those programs have not shown a positive effect.

In Nashville, for instance, Springer looked at a merit pay program for math teachers.

SPRINGER: So basically we had 300 teachers volunteer in middle school mathematics. Half were assigned to a control group, which is life as usual. The other half were eligible to earn up to a $15,000 bonus per year for a three-year period, so potential $45,000. We found no effect.

The bonuses also had no impact on how teachers taught, approached curriculum or interacted with parents.

But just because studies have shown merit pay has no effect, Springer doesn’t think we should stop experimenting with how we pay educators.

SPRINGER: We can design incentive pay programs in any number of ways. We may see variation in what the minimum or maximum bonus award may be. We may see variation in the threshold that a teacher or an administrator needs to hit in order to receive an award.

It’s been reported that about 4 percent of school districts nationwide have some sort of merit pay. Some 180,000  teachers in Texas got a bonus this year linked to their performance review.

But some of the nation’s largest efforts have been curtailed or canceled recently due to budget cuts. And due to evidence like Springer’s.

Chicago’s effort is being paid for through $5 million dollars in private donations—including a million dollars from Board of Education member Penny Pritzker and her husband.

Springer says it’s critical that districts setting up merit pay programs get independent researchers to evaluate what they’re doing.

SPRINGER: Because without the research, and without an independent group evaluating these programs, we’re not going to know whether they’re effective and whether it is an efficient allocation of our resources.

Chicago has no evaluation of its principal bonus program planned at this time.

Not everybody thinks we need to change the way educators are paid. The current system protects teachers against bad or biased bosses who could determine arbitrarily which teachers are better.  It guarantees women the same pay as men.

And while Springer thinks the way educators are paid is broken, he says the research on merit pay still hasn’t yielded a better way.