Study: NBPTS Teachers Produce Only Tiny Gains

Published November 1, 2004

Soon the education world will have a mass of reports to digest on the relative effectiveness of teachers who receive certification from the National Board for Professional Teaching Standards (NBPTS).

Under fire for the lack of research during its first 17 years on the impact of National Board Certified Teachers (NBCTs) on student achievement, the NBPTS has commissioned more than 20 such studies.

Judging from the results of an early study, however, a consensus in the research community may be a long time coming. Education researchers at Arizona State University compared the academic performance of elementary students taught by 35 NBCTs in 14 Arizona school districts with that of students of non-NBCTs. Leslie G. Vandevoort, Audrey Amrein-Beardsley, and David C. Berliner looked at four years of Stanford Achievement Tests data and published their results on September 8 in the journal Education Policy Analysis Archives (EPAA). They found:

  • In about one-third of 48 comparisons, students taught by NBCTs scored higher, by statistically significant margins, than students taught by non-NBCTs.
  • A measure of the size of the effect, translated into grade equivalents, showed the gains for students of NBCTs were about one month greater than gains made by non-Board-certified teachers.

The authors conceded, “this study does not address whether other, cheaper, or better alternatives to the National Boards exist, as some critics suggest.” They nevertheless asserted that “the results of this study provide support for the policies in many states that honor and provide extra remuneration for National Board Certified Teachers.”

Professor J.E. Stone, founder of the Education Consumers Clearinghouse and author of a value-added analysis that found Tennessee’s 16 NBCTs did not do significantly better in advancing student achievement than did non-NBCTs, pointed out that according to the Arizona researchers’ own calculations, two-thirds of the differences between NBCTs and “ordinary garden-variety” teachers were not statistically significant.

The most telling point, Stone said, was the finding of an average “effect size difference” of just .12–an estimated one month achievement gain. By contrast, the achievement gaps between the groups identified by the No Child Left Behind law are often one or two years.

“Do policymakers understand that they are paying $7,500 or more per year for an added one month of achievement gain?” asked Stone, referring to the bonuses often paid teachers who win National Board certification.

The Arizona State researchers took the unusual step of flinging challenges at prominent researchers who have noted the lack of proof that NBPTS is worth the large public subsidies it has received from the federal and state governments and private foundations. For instance, they suggested that Michael J. Podgursky, economics professor at the University of Missouri/Columbia, might now reconsider his published conclusion that “no rigorous study” had ever been published to show students of NBCTs learn more.

Asked for comment, Podgursky was not ready to proclaim the Arizona State study a show stopper.

“The results of the study are mixed,” he said. “In some cases, students of Board certified teachers have significantly larger gains, whereas in others they do not. In addition, the researchers do not have adequate controls for student SES [socioeconomic status]. It may be that the National Board teachers are in classrooms with higher SES students within a school district. That may account for the difference in gain scores.

“This study is a step in the right direction in terms of research. But we need more studies of student achievement gains, with rigorous controls for student SES, before we confidently assess how well National Board certification identifies superior teachers. In addition, the study did not address whether there are other, less costly ways to identify superior teachers. That is an important question that needs to be addressed as well.”

An education research expert at the University of Virginia, psychology professor Daniel T. Willingham, cited flaws in the study’s methodology–in particular the lack of the correct control group. Teachers who seek national certification, he pointed out, are a self-selected, motivated group.

“Unless you think you’re a pretty good teacher, you wouldn’t try for it,” he said.

Therefore, “the proper control group to compare to certified teachers would not be ‘others,’ but would be teachers who tried for certification, but didn’t get it,” Willingham continued. “That would show that certification is really separating the better teachers from the less competent.

“The authors don’t seem to have done that. They compared certified teachers to the rest of the population. Are the certified teachers better? Based on their data, probably, although it’s hard to tell because they didn’t analyze their data properly. Did the process of certification really tell you anything? From these data, it’s impossible to tell.”

Robert Holland ([email protected]) is a senior fellow at the Lexington Institute, a think tank in Arlington, Virginia.

For more information …

The 117-page article, “National Board Certified Teachers and Their Students’ Achievement,” by Leslie G. Vandevoort, Audrey Amrein-Beardsley, and David C. Berliner, is available online in the September 8, 2004 issue of the Education Policy Analysis Archives at