Researchers have found, again, that offering teachers extra money to boost their students’ test scores doesn’t have any measurable impact on teacher performance.

The latest study, this one the first ever controlled study on the controversial issue, came from the National Center on Performance Initiatives at Vanderbilt University. Matthew Springer, NCPI’s executive director, said the results showed that pay-for-performance initiatives, alas, are not "the magic bullet that so often the policy world is looking for."

NCPI got a set of 296 Nashville middle school math teachers to agree to take part in the study where half were randomly placed in a control group while the other set was promised $5,000, $10,000 or $15,000 if their students’ scored well on a Tennessee standardized test. One third of the teachers got a bonus at least once in the course of the three-year study, while eighteen teachers received bonuses every single year. And yet, researchers found no measurable difference in students’ test scores. Students taught by teachers who were promised bonuses progressed no faster than their peers in the control group.

The study reinforces the argument that teachers don’t have a secret stash of tricks, tools,  and skills that they secret away but bring out at the promise of more money. Critics of the pay scheme argue that merit pay alone doesn’t make teachers better. And no teacher would ever scoff at a higher salary, but very often pay-for-performance initiatives come at the cost of teacher tenure and other benefits.

The findings were important for other political reasons. For one, pay-for-performance initiatives are a a central part of the Obama administration’s education agenda. Secretary of Education Arne Duncan gave billions of dollars to states who won the Race to the Top competitive grants program. Many states that won were successful because they had adopted similar models that tied a teacher’s salary and job security to how well their students performed on test scores. Education advocates criticize Duncan’s schemes as being a continuation of George W. Bush’s failed No Child Left Behind bill that placed standardized test scores at the center of education. And Duncan’s critics say the education reform movement has modeled its reforms on a corporate business structure–indeed, many of the superintendents and policymakers calling the shots in the education world today are business people with no classroom experience. Benchmarks, quotas and bonuses may work for improving account managers’ performance, but they don’t necessarily translate so well when it comes to the work of educating kids in classrooms.

And the study, received like a bombshell in the education world, shows just how little information and data the education reform world has on the ideas that the Obama administration is encouraging school districts to adopt. In 2009 Vanderbilt University researchers found similar results with a pilot incentive pay program in Texas. But this week’s is just the first controlled study on the matter, and as always the researchers stress the need for more evaluation, but it’s an important, if damning report.

And yet the education reform train keeps barreling down the tracks; it’s a hard thing to stop.