Tiny Gains Trigger Large PR Effort by National Teacher Certifiers

Published January 1, 2005

The National Board for Professional Teaching Standards (NBPTS) is touting the results of a new study as proving that its performance-based system of national certification identifies effective teachers who deserve rich bonuses because their students show substantial achievement gains.

Critics say there’s less evidence than the high-powered PR from the NBPTS would suggest. The study author’s preferred model shows an average achievement gain–or “effect size”–of just 7.4 percent of a standard deviation.

The study–of math tests taken by ninth- and 10th-grade students in Miami-Dade County, Florida public schools–found that National Board Certified Teachers (NBCTs) helped their students to larger testing gains than did teaching colleagues who lacked the certification.

A news release on the NBPTS Web site says chief researcher Linda Cavalluzzo of the nonprofit CNA Corporation’s Education Center isolated the effects of NBPTS certification from other factors (such as teacher experience and education, per-pupil spending, and previous levels of student achievement) that might affect test scores.

“This study should put to rest many of the doubts that well-intentioned skeptics may have harbored about National Board Certification’s ability to pinpoint what makes an exceptional teacher,” said NBPTS Chairman Roy Barnes, former governor of Georgia. He added, “we are left to conclude” that certification “is indeed a true and valid indicator of teaching excellence.”

Cavalluzzo asserted that if parents asked “What class do I want my child in?” the answer should be “you want your child in a class taught by an NBCT.”

Achievement Advantage Is Small

However, data in the study itself, not cited in the NBPTS release, appear to produce results far more ambiguous.

While NBCTs may produce gains that are “robust” (i.e., repeatable) and “statistically significant” (i.e., non-random), the size of the average gain is very small. Using Cavalluzzo’s preferred model, teachers with National Board Certification showed an average achievement gain of just 7.4 percent of a standard deviation when compared to otherwise similar teachers. Another recent NBPTS-sponsored study reported similarly small gains for NBCTs. (See “Study: NBPTS Teachers Produce Only Tiny Gains,” School Reform News, November 2004.)

Also, the report’s Table 2 (page 18) shows that the achievement gain for NBCTs was 66.70, while the achievement gain for Miami-Dade math teachers who had no involvement with NBPTS was 65.45. That is a mere 1.25-point difference on a score scale ranging into the thousands.

That 1.25-point advantage contrasts with the 159-point gap in prior test scores between students taught by the NBCTs and average students in the Miami-Dade school system. Critics suggest that shows how trivial the purported gain is relative to the magnitude of the problem.

Price Paid Is High

“Is this what policymakers thought they would be getting when they committed to 10 percent salary increases and a $5,000 bonus?” asked East Tennessee State University Professor J. E. Stone, who conducted his own study indicating Tennessee’s NBCTs did not perform significantly better than other teachers in advancing student achievement. (See “Nationally Certified Teachers Come Up Short on Achievement,” School Reform News, August 2002.)

In practical terms, explained Stone, this result means that if all 1,947 ninth- and 10th-grade math teachers in the Miami-Dade School System became NBPTS certified, math scores would presumably rise by only 1.25 points. However, he continued, with the 10 percent salary increase and $5,000 bonus that are awarded for NBPTS certification, “the cost would be in the neighborhood of $15 million.

“Whatever else can be said about NBPTS certification,” commented Stone, “it is becoming increasingly clear that is not a cost-effective means to improved student achievement.”

The data also indicate that the NBCTs started with the best students and taught in the best schools. Even if the study showed they led students to praiseworthy gains under those conditions, it does not necessarily follow those teachers would be as effective were they assigned to schools with the disadvantaged students who are most in need of help.

Under such circumstances, NBCTs might be below-average teachers. Research by the late Jeanne Chall of Harvard, among others, shows student-centered pedagogy (which NBPTS favors in evaluating teachers for certification) helps such students far less than do structured, teacher-centered methods.

Stone and other researchers said it was not clear exactly how Cavalluzzo had conducted her statistical analysis and expressed interest in gaining access to the Miami-Dade data to conduct their own studies. The data set used by Stone in his NBPTS study, for example, is freely available so that other researchers can replicate his work.

However, Cavalluzzo told School Reform News the data she used was “proprietary” and belonged to the Miami-Dade district.

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

For more information …

The November 2004 report from the CNA Corporation, “Is National Board Certification An Effective Signal of Teacher Quality,” by Linda C. Cavalluzzo, can be found at http://www.cna.org/documents/CavaluzzoStudy.pdf.

Other CNA reports on education are available at http://www.cna.org/expertise/education.

The NBPTS news release on the study can be found at http://www.nbpts.org/news/article2.cfm?id=551.

Robert Holland’s August 2002 School Reform News article, “Nationally Certified Teachers Come Up Short on Achievement,” is available at http://www.heartland.org/Article.cfm?artId=1033.

Robert Holland’s November 2004 School Reform News article, “Study: NBPTS Teachers Produce Only Tiny Gains,” is available at http://www.heartland.org/Article.cfm?artId=15821.