While crafting the state budget last year, the North Carolina General Assembly applied the latest empirical research to the question of how best to improve teacher quality. In response, lawmakers have been roundly excoriated by the usual suspects — which only served to demonstrate that the public-policy acumen of the usual suspects is, uh, suspect.

For decades, North Carolina gave salary supplements to teachers who acquired graduate degrees. Our state wasn’t alone. The practice became increasingly common in the 1980s and 1990s as states created “career ladders” and other pay plans intended to enhance teaching quality and performance.

Perhaps the idea was worth a try. It seemed plausible that teachers with advanced degrees might be more effective than other teachers, either because of the content of their graduate programs (almost always at schools of education) or because the ability to do graduate-level work might correlate with the ability to teach students.

But the idea didn’t pan out. It was a colossal flop, wasting hundreds of millions of tax dollars while doing nothing to enhance student learning.

Don’t take my word for it. Salary bumps for teachers with graduate degrees has become one of the most-studied education reforms in modern times. Just since 1990, there have been at least 86 studies published by academic journals or the National Bureau of Economic Research that either examined teacher-education supplements directly or used the share of teachers with graduate degrees as a control variable for explaining student achievement.

Few reforms have yielded clearer, albeit disappointing, results. In 70 of those 86 studies, there was no clear, statistically significant relationship between student outcomes such as test scores or graduation rates and their teachers possessing graduate degrees. In four studies, the relationship was negative. So in just 12 studies, 14 percent of the total, did students do better when their teachers had graduate degrees.

Compare this to another idea that became popular in the 1980s and 1990s: giving salary supplements to teachers certified by the National Board for Professional Teaching Standards. Former Gov. Jim Hunt was one of the originators of this idea, which helps to explain why North Carolina has a disproportionate share of the nation’s board-certified teachers.

Although board certification hasn’t been studied nearly as much as graduate degrees for teachers, the available evidence is still modestly supportive. Nine of the 17 academic studies published to date show that students of board-certified teachers perform at least a little better than comparable students in other classrooms.

So the General Assembly didn’t get rid of North Carolina’s salary supplements for board certification. But it did end the pay boosts for graduate degrees. The recurring savings will be about $19 million. What did lawmakers do instead? For one thing, they set aside $10 million a year to give performance-based pay raises to the state’s best teachers. They also spent about $1 million enhancing the state’s value-added assessment system to give principals and superintendents better information about teacher effectiveness and another $7.5 million to fund North Carolina’s adoption of rigorous, independent testing of high school students with the ACT and related assessments.

Each of these policy decisions had empirical support. Most academic research shows that rigorous testing is critical to the educational success of states and nations, and that value-added assessment of teachers yields valid information for use in staff development, employment, and compensation decisions. As for pay policies in America or around the world that reward teachers for gains in student achievement, 14 of the 23 studies published since 1990 show positive, statistically significant results. Among the 10 studies looking at performance bonuses at the school level, rather than for individual teachers, seven show positive results.

Ditching graduate-degree supplements in favor of rigorous evaluation and performance pay was a wise decision. Yes, the critics continue to fume, particularly those who work in the schools of education that awarded the vast majority of the graduate degrees in question (and were thus prime beneficiaries of the old system). State lawmakers should hold firm. They got it right the first time.

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Hood is president of the John Locke Foundation.