What makes a good teacher?

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Which teacher credentials make a difference in the classroom? It’s a research question with significance for districts who recruit teachers, for the principals who hire them and for a public concerned with teacher quality.

Unequal distribution of the teachers with the best credentials became a contentious issue in Chicago earlier this year. The Education Trust released a study that found that Chicago teachers who were rated lowest in experience, education and academic aptitude were concentrated in low-income, minority neighborhoods.

CPS has begun taking some steps toward easing the inequities. It recently won a federal grant aimed at luring teachers to low-performing schools with cash incentives for raising test scores.

Stepped-up recruiting efforts have raised the percentage of new hires with master’s degrees from 34 percent to 40 percent over the last two years. And in October, Mayor Richard M. Daley announced the district had set a goal to have 10 percent of teachers earn certification from the National Board for Professional Teaching Standards. (Nationally, only about 1 percent of teachers have board certification.)

But a teacher’s credentials—education, experience, test scores or any other measurable characteristic—actually predict only a small percentage of the impact that they have on student achievement. Researchers believe measurable characteristics only account for 10 percent or less of the gains students make on standardized tests.

That leaves more than 90 percent of teacher quality—as defined by test score gains—unaccounted for by any measure available to policy makers, says Daniel Goldhaber, a professor at the University of Washington’s Evans School of Public Affairs in Seattle.

Research can’t capture the intangible teacher qualities—such as motivation or presentation—that apparently make a far bigger difference in student learning than their credentials, he explains.

Here is a round-up of local and national research on the characteristics that make a difference to student achievement.

Individual teachers matter most

While credentials appear to only have a modest impact on student achievement, the skills of individual teachers make an enormous difference, researchers say.

In a single year, students with the worst teachers made a half-year’s worth of reading gains, while those with the best teachers gained a year and a half, according to a study of children in Gary, Indiana by Eric Hanushek of Stanford University.

A 2003 study by the Federal Reserve Bank of Chicago found a six-month gap in math test score growth between Chicago freshmen who had teachers ranked in the top third of those studied, as compared to those in the bottom third.

The gap between similar students who had three effective teachers in a row versus three ineffective ones amounted to a whopping 50 percentage points on the Iowa Test of Basic Skills, according to statistician William Sanders’ analysis of student data in Tennessee. (Sanders created Tennessee’s “value-added” assessment system, which measures test score growth.)

The studies defined good or effective teachers as those who raised test scores the most, while those who raised scores the least were deemed ineffective. The conclusion: It’s clear that the personal characteristics of individual teachers have a substantial impact on student achievement, but what those characteristics are remain unclear.

National Board certification

CPS is pushing National Board certification, and teachers who earn the prestigious credential do produce higher test score gains than those who failed or did not attempt the rigorous certification process, a number of studies concluded.

But researchers disagree on whether the differences between the groups are significant.

Sanders calls the differences so slight, they’re “about the thickness of your thumbnail.” His analysis of 260,000 student records in two North Carolina districts found that many nationally certified teachers proved among the least effective in raising scores. Meanwhile, some of the most effective teachers were not nationally certified. (His analysis controlled for student characteristics, including poverty.)

The chance that a teacher with National Board certification is more effective than one without is “only slightly better than a coin flip,” says Sanders.

Goldhaber studied a similar group of North Carolina teachers but found better results for those with National Board certification. Their students gained seven to 15 percent more on standardized tests compared to teachers who tried and failed to earn certification.

Still, “there are a lot of [nationally] certified teachers who are not as good as the average teacher,” Goldhaber acknowledges.

“That’s going to be true no matter what type of credential you look at,” he adds. “The credential may be predictive, but it doesn’t mean that everybody with that credential is going to fit the prediction.”

College selectiveness, test scores

Teachers who attended highly selective colleges or universities as undergraduates appear to produce higher academic gains in students, particularly in high school students, according to a research review by the Economic Policy Institute.

Having a teacher who attended a prestigious college seems to make an even greater difference for black students than for white students, according to a study co-authored by Ronald Ehrenberg, director of Cornell Higher Education Research Institute at Cornell University in New York. Ehrenberg speculates that black students in the study may have been more likely to come from single-parent households, or have a parent with less education, and thus received less support at home. Teacher quality is likely to be more important for children who get less home support, he adds.

“Basically, it’s important to get our best and brightest people into the classroom,” he says.

Teachers who score better on tests of literacy or verbal skills also produce higher gains in student test scores, according to a number of studies.

One study that analyzed the school records of African-American students in Gary, Indiana found that teachers with higher verbal skills produced higher gains on reading tests. Another study of Alabama schools found that teachers’ ACT scores were associated with higher test score gains in reading; the study found mixed results for math scores.

College coursework

Teachers are expected to earn master’s degrees—and are paid more for doing so—but that extra credential is not associated with higher student test score gains, except for high school math and science teachers who hold master’s degrees in those subjects, according to the Economic Policy Institute.

The Federal Reserve Bank of Chicago study on CPS high school math teachers found that freshmen made an extra month of progress on standardized math exams when teachers had majored in math, science or education as undergraduates.

Another study found that high school math and science teachers who had taken subject-specific coursework appear to raise the achievement of high school students, up to a point. Those gains taper off after teachers have completed a certain number of college courses in their subject area. However, additional courses on how to teach their subject continued to boost achievement.

“Its one thing to know mathematics, but it’s another thing to understand how learners acquire that knowledge,” explains David Monk, dean of the College of Education at Pennsylvania State University, who co-authored that study. “The main message is that both are important.”

Teacher experience

Students with inexperienced teachers are at a disadvantage, a number of studies have found. Texas elementary school students gained significantly less on standardized math tests under first-year teachers, and slightly less under teachers in their second or third year, according to one study. In Chicago, freshmen with first-year math teachers also made smaller gains, according to the report by the Federal Reserve Bank of Chicago.

Researchers have generally not found that teaching experience beyond a few years influences student achievement. But it may be impossible to establish that fact conclusively without considering that teachers hired during economic boom times, when jobs are plentiful, may be less effective than those who had to compete when teaching jobs were scarce. So far, researchers have not examined that, according to a 2003 study in the Review of Education Research.

Overall, while credentials predict only a very small portion of teacher’s eventual success or failure, that doesn’t mean that the distribution of teachers with master’s degrees or experience is irrelevant, Goldhaber says.

It’s statistically unlikely that the real differences in teaching skill are any more equitably distributed between high and low income neighborhoods, he says. “That would be surprising.”

To contact Elizabeth Duffrin, call (312) 673-3879 or e-mail duffrin@catalyst-chicago.org.