The most rigorous study of performance-based teacher compensation  ever conducted in the United States shows that a nationally watched  bonus-pay system had no overall impact on student achievement—results  released today that are certain to set off a firestorm of debate.    
Nearly 300 middle school mathematics teachers in Nashville, Tenn.,  voluntarily took part in the Project on Incentives in Teaching, a  three-year randomized experiment conducted by researchers affiliated  with the National Center on Performance Incentives  at Vanderbilt University. It was designed to study the hypothesis that a  large monetary incentive would cause teachers to seek ways to be more  effective and boost student scores as a result. 
    But it yielded only two small positive findings, limited to 5th  graders in the second and third year of the experiment. No effects were  seen for students in grades 6-8 in any year of study.
    At the same time, however, participating teachers did not report  finding the pay program’s goals for students out of reach or its impact  on school culture damaging, two concerns that have been among those  voiced by opponents of performance pay.
    The implementation of the pay program “did not set off  significant negative reactions of the kind that have attended the  introduction of merit pay elsewhere,” the study’s authors write. “But  neither did it yield consistent and lasting gains in test scores. It  simply did not do much of anything.”
    The findings arrive in a highly charged teacher-quality policy  environment, in which many states and districts, with support from the  Obama administration, are overhauling current practices for preparing,  evaluating, and compensating teachers. 
    And they come at a particularly inopportune time for the U.S.  Department of Education, which is scheduled to announce a fresh slate of  grantees this month under a federal program designed to seed merit-pay  programs for teachers and principals. 
   Union Cooperation 
    The study, known as POINT for the Project on Incentives in  Teaching, was designed by the researchers, with the input of the  76,000-student school district and the support of the local teachers’  union affiliate and the Tennessee Education Association. Matthew G.  Springer, the director of the Nashville-based center, cited the unions’  cooperation as a crucial factor in the study’s successful  implementation.
    The executive director of the Tennessee Education Association said  the reputation of the researchers played an important role in the  union’s decision to sign on. “We thought it was a chance to work with  researchers whose processes and reputation we trust, and they were  coming at this question with no particular ideology,” said Al Mance. “We  said, ‘OK, this is something we really want to know. We won’t have a  better opportunity than this.’ ”
    The program was instituted in Nashville between 2006-07 and 2008-09 and covered 296 middle school math teachers in grades 5-8. 
    Participating teachers, all volunteers, were assigned to either a  treatment group eligible to receive significant pay bonuses or a control  group earning normal wages. Those in the treatment group were rewarded  with bonuses between $5,000 and $15,000 based on whether their students’  achievement rose by a specified amount over the course of a year. The  gains were calculated using a value-added methodology designed to filter  out other aspects that could have influenced the scores.
    The teachers were also randomized in clusters, so that there was  at least one treatment and one control teacher in every middle school.  And the program contained no quotas, so all teachers whose students  performed at the specified targets earned the additional pay. 
    Over the course of the study, attrition reduced the number of  participating teachers to only 148, and researchers carefully tracked  that pattern over time to make sure it did not change the equivalence of  the two groups in such a way as to skew the results. Only one teacher  withdrew from the study; most of the attrition occurred because teachers  were reassigned or left the district.
    On average, students taught by the teachers taking part in the  program did not make larger academic gains than those taught by teachers  in the normal wage group.The sole exception was in grade 5 in the  second and third years of study. 
 In those years, the incentive pay was linked to  statistically significant increases in student scores—an increase, the  report states, equal to between a third and a half year of learning. But  the effect did not appear to persist.
    “By the end of 6th grade,” the study states, “it does not matter whether a student had a treatment teacher in grade 5.” 
    The researchers performed a number of tests to try to make sense  of the grade 5 findings, including to see whether there was evidence of a  reallocation of time from other subjects to math, or cheating on the  exams. But none of them turned up any firm explanation.
    “It really is puzzling,” said Mr. Springer. “It just raises  questions about what’s different about 5th grade and what factors played  a role. Was it student development? The curriculum? Teaching or  classroom structures?”
       In interviews, scholars who study performance-based pay and  teacher incentives and who were familiar with the POINT findings but not  involved in the experiment, widely praised its rigorous design.  
    “It’s a really well-designed study, and it’s really important  because a lot of the debate about performance pay has been  evidence-free,” said Steven N. Glazerman, a principal researcher at  Mathematica Policy Research, a Princeton, N.J.-based evaluation firm.
    The existing empirical research literature on incentive pay has been limited in scope, size, and relevance. Much of the experimental research concerns programs in other countries.
    What’s more, many of the existing performance-pay programs  studied in the United States award far smaller bonuses, and scholars  have questioned whether those amounts were enough to affect a change in  teacher behavior.
    But the POINT findings, said some researchers and advocates,  appear to put to rest the idea that incentive pay in and of itself is  enough to spur better teacher performance.
    “A lot of the discussion about performance pay is based on a  faulty assumption that the reason we don’t have higher test scores is  that teachers are shirking their responsibilities,” said Helen F. Ladd, a  professor of public policy and economics at Duke University in Durham,  N.C., about the findings.
    Ms. Ladd added, however, that she was “a little surprised” that  the findings were not more mixed. She anticipated that teachers might  work even harder over the short term to win bonuses. But that  supposition was not borne out by the study. 
    Mr. Mance of the Tennessee Education Association said the study  confirms what many teachers and unions have long believed: that teachers  are already hardworking. For this study to show positive results, he  said, “you’d have to have teachers who were saving their best strategies  for an opportunity to get paid for them, and that is an absurd  proposition.” 
    Researchers cautioned, however, that the Nashville experiment does  not provide answers to many other questions about incentive pay. For  instance, it wasn’t designed to test the hypotheses that pay incentives  might serve as a draw to a different population of teacher-candidates or  as an incentive for other candidates to stay in the profession—thus  potentially changing the quality of the teacher workforce.
    “I personally believe that the biggest role of incentives has to  do with selection of who enters and who stays in teaching—how incentives  change the teaching corps through entrance and exits,” said Eric A.  Hanushek, a professor of economics at the Hoover Institution at Stanford  University. “The study has nothing to say about this.”
    And because the study looks at an incentive program strictly as  pay, it remains unclear how far the findings can be extrapolated to  incentives with more features, such as professional development,  differentiated roles, or a new teacher-evaluation system.Many well-known  incentive-pay models, including Denver’s ProComp system and the popular  Teacher Advancement Program, sponsored by the Santa Monica,  Calif.-based National Institute for Excellence in Teaching, contain such  elements.
ver the use of test scores  as a measure of student learning and teacher effectiveness remains a top  concern for teachers. Surveys of participants for POINT found that a  majority generally supported higher pay for teachers whose students made  achievement gains. Yet in 2009, about 85 percent said they felt the  test-based criteria for determining effectiveness were too narrow. 
    That lack of buy-in, the study’s authors postulated, might have  contributed to the finding of no differences in how the control and  treatment groups affected instruction.
   Inopportune Moment
    From a policy perspective, performance pay has experienced a type  of renaissance over the past six years, following the introduction in  2004 of the ProComp and in 2006 of the federal Teacher Incentive Fund,  or TIF, a program established under the administration of President  George W. Bush to seed performance-pay systems.
    Since 2008, the Obama administration has embraced TIF and has put  its own stamp on performance pay through the Race to the Top  competition, which encouraged states to institute new systems for  evaluating teachers and for using the results of those evaluations to  inform pay decisions.
    “While this is a good study, it only looked at the narrow question  of whether more pay motivates teachers to try harder,” a spokeswoman  for the U.S. Department of Education said in an e-mail. “What we are  trying to do is change the culture of teaching by giving all educators  the feedback they need to get better while rewarding and incentivizing  the best to teach in high need schools and hard-to-staff subjects.”
    The effects of the report on that policy agenda are not clear, but  in the short run at least, proponents of merit pay are likely to steer  clear of replicating the features of the Nashville program.
    “Anyone about to implement a performance-based pay system will  want to pay very close attention to this study, to learn from the POINT  program’s successes, but especially its shortcomings,” said Mr.  Glazerman of Mathematica. “These groups bear a heavy burden to figure  out how their own programs can demonstrate a greater impact than what  we’ve seen so far.”
    “I think most people today agree that the existing compensation  structure for teachers is broken, but we don’t know what a better way  is,” added Mr. Springer of the Vanderbilt center. “This experiment is  one step in the right direction in terms of building our knowledge base,  but we need to continue to build that base and test other program  designs.”