Do teacher characteristics such as academic achievement, years of experience, and certification affect student test scores?

Most of these characteristics have been examined using large sets of data in which teachers are linked to student scores. Several of the characteristics do indeed bear a relationship to student achievement, but in general, scholars say their effects tend to be somewhat weak or inconsistent across studies.

Thus, on average, such characteristics matter. But there are plenty of cases in which teachers with advanced degrees, extensive experience, or specialized credentials are not noticeably more effective than their peers, and there are likewise many effective teachers without such credentials.

The basic problem can be summed up by the conclusion of a study dating from 2005. It found large differences among teachers in terms of their value-added impact on student achievement and went on to note that this variation was not readily explained by factors such as graduate degrees or experience after the first few years in the profession.[1] A 1999 paper, meanwhile, estimated that only 3 percent of the variation in student achievement could be traced back to measurable teacher characteristics, such as teachers’ academic profiles and degrees.[2]

Of these measures, there is good evidence that teachers gain in effectiveness with additional years on the job.[3] In general, value-added analyses show early career experience pays off in effectiveness steadily through at least the fifth year. This effect appears to be more consistent for elementary and middle schools than for high schools.[4] In addition, the impact of experience appears to be stronger than that of most other teacher characteristics.[5]

Reviews of the empirical research on credentials, in general, point to consensus that teachers’ math content knowledge seems to improve students’ test scores in that subject.

One study found this connection at the 1st and 3rd grade levels using a specially constructed measure of pedagogical content knowledge.[6] A second study looking at Florida test data found links between content-focused professional-development credits in math and secondary math achievement.[7] And one study found slight boosts in achievement for middle and high school students taught by teachers with an undergraduate or graduate degree in mathematics.[8]

Information on other content areas is sparse, but one study found a link between teachers’ holding a bachelor’s degree in science and student achievement in that subject. [9]

Studies are mixed on the attainment of advanced degrees and elementary-level student achievement; some studies show positive correlations, others negative ones. On balance the link to achievement is likely tenuous at best.[10] Several studies have found that entering teaching with a master’s degree of any kind does not boost achievement, relative to not holding such a degree, nor does earning such degrees seem to improve outcomes at the elementary level.[11]

Licensure test scores seem to matter more for math than for other subjects. They consistently appear linked to improved student achievement in that subject, at both the elementary level and at the high school level for algebra and geometry. Findings are mixed for other subjects.[12]

As for certification, one study found that students taught by teachers with any sort of certification outperformed those without certification or who were certified out of field.[13] Another found that those taught by teachers with standard certification outperformed uncertified teachers or those with nonstandard certifications.[14]

Much of the information on teacher certification also seems to find benefits primarily for math. At the high school level, teachers with subject-specific credentials in math tended to boost students’ scores more than those teachers who were not certified in that subject.[15]

Scholars have noted that teachers may affect learning more in mathematics, which tends to be taught exclusively in school, than in reading.[16]

Scholars have spent much time analyzing the effects of National Board Certification, but these numerous studies have mixed findings. In a review of the literature, a National Research Council panel concluded that evidence supports the notion that students taught by national-board-certified teachers on average have higher scores than those not taught by such teachers. But it said the evidence doesn’t support the idea that the process itself makes teachers better at their craft.[17]

Teachers who enter the profession with specific sets of cognitive and noncognitive skills also on average seem to be slightly more effective than those who do not.[18]

The policy implications of these findings are, again, hard to parse. Generally speaking, the policy question concerns whether investing in certain teacher characteristics, (by paying a premium for teachers who hold National Board Certification or a master’s degree, for instance), are cost effective relative to other possible investments.

For a longer summary of the research literature on credentials, see Goe 2007.

It can be said:

Teachers improve in effectiveness at least over their first few years on the job. Characteristics such as board certification, and content knowledge in math sometimes are linked with student achievement. Still, these factors don’t explain much of the differences in teacher effectiveness overall.

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