Teachers often say they don’t do their jobs for the money, but surely financial incentives are a factor in just about any career decision. Would you work harder at your job if there was a cash bonus on the line? More importantly, would the extra money alone somehow make you a more effective employee?

Under a new law being implemented over the next several years in Indiana, student test scores will now be used as a factor in whether a teacher receives a pay increase.  The Indianapolis Star, in partnership with The Hechinger Report, is closely monitoring the state’s reform measures aimed at boosting teacher effectiveness.

The state’s teachers are questioning whether the law can be fairly applied, and whether merit raises will ultimately result in students learning more, according to the recent entry in the newspaper’s series. There are also fears among educators that the unpredictability of the pay scale will discourage people from considering teaching as a career.

“The level of concern from our teachers is through the roof,” Wayne Township Superintendent Jeff Butts told the Star. “It’s higher than I’ve ever seen it.”

Schools districts across the country continue to tinker with merit pay, despite a dearth of evidence showing it’s an effective tool for reform.  Boston Public Schools is exploring whether offering cash bonuses to faculty helps boost student achievement, handing out more than $400,000 in the first round of cash incentives to teachers and staff at schools that made gains on standardized tests.

Armed with sizable federal grants intended to spur reform and improve student learning, dozens of states are experimenting with incentive pay using a wide range of formulas. In some schools, individual teachers earn bonuses based on the progress of their students. Other districts, like Boston, reward the entire staff for overall achievement.

The Boston teachers union president, Richard Stutman, says his organization supports the all-for-one, one-for-all approach to incentives. “Individual rewards set up an unnatural competitiveness in schools and leads to a potential divisiveness and a potential lack of sharing of best ideas among teachers,” Stutman told the Boston Globe. “Teachers work hard regardless of a reward.”

The District of Columbia Public Schools rewards teachers, sometimes with as much as $25,000, for successive years of achievement. As Jason Kamras, DCPS’ chief of human capital, recently told the New York Times, “We want to make great teachers rich.”

What’s not yet clear is whether such bonuses will improve student learning. The National Center on Performance Incentives at Vanderbilt University looked at three years of data from Nashville’s public schools and concluded that a merit pay pilot program had little or no effect on instruction or student achievement.

The Nashville pilot program, where teachers could earn up to $15,000 for improved student test scores, “was focused on the notion that a significant problem in American education is the absence of appropriate incentives, and that correcting the incentive structure would, in and of itself, constitute an effective intervention that improved student outcomes,” according to the report’s executive summary. However, “results did not confirm this hypothesis,” according to the researchers.

The notion that teachers might work more effectively if they know there’s a cash reward at the finish line is an interesting one. (Stutman, the Boston teachers union chief, told the Globe he doubted it was a motivating factor.)  But how many other professions use merit pay to push performance, and does it work?

A 2009 report on teacher performance pay and accountability from the Economic Policy Institute in Washington, D.C.,  found that “relatively few private-sector workers have pay that varies in a direct, formulaic way with their productivity, and that the share of such workers is probably declining.” Merit pay systems in the private sector have been found to hurt job performance, rather than improve it, the report concluded. The researchers also make the case that student test scores are not a reliable measure of how well teachers do their jobs.

If that’s the case, then why are so many policymakers willing to bet that extra money will improve teacher — and as a result, student — performance?