Political debates about education policy are so contentious that consensus may seem forever out of reach. Yet here’s something that virtually everyone agrees is true: academic achievement reflects more than just the value added by teachers, administrators, textbooks, and technology. Student characteristics and family background correlate strongly with outcomes.

This is a statistical fact. But we need not interpret it fatalistically. To say that students from disadvantaged backgrounds tend to face greater challenges in school is not to say they can’t learn, or that particular public policies can’t improve the likelihood of success in teaching those students.

Keeping that in mind, which public school systems exhibit the greatest success in helping disadvantaged students achieve proficiency?

For interstate comparisons of academic performance, the gold standard of measurement is the National Assessment of Educational Progress. Since the early 1990s, NAEP has tested samples of students in most states in core subjects. There are periodic exams of 4th and 8th graders, as well as a national sample of 12th graders that doesn’t produce state subsamples.

I recently took a look at the 2011 8th-grade NAEP exams for reading, math, and science. In each case, I made a list of the states where the average scale score was higher than for the country as a whole. Differences of only a point or two don’t count, given the nature of sampling. Fortunately, NAEP identifies the gaps there are statistically significant.

Some states score high in reading but not math, or high in math but not science. So I zeroed in on the states that exceeded the national average in all three subjects. There were 18 such states in 2011. North Carolina was not among them. In fact, the only Southern state that made the cut was Virginia.

However, the problem with ranking states by overall scores or proficiency percentages is that the ranking may tell us more about the composition of the test-taking population than about how much value each state’s school systems add to the mix. Indeed, most of the 18 high-achieving states on the NAEP are in the Northeast, Great Plains, or Mountain West, and thus tend to have lower-than-average rates of child poverty or other disadvantages.

So the next step was to confine the data to scale scores of students eligible for free or reduced lunch, a standard proxy for lower-income status. That excluded eight states from the list, leaving 13. Here are the states with the highest scores for lower-income students: Idaho, Kansas, Maine, Massachusetts, Minnesota, Montana, North Dakota, New Hampshire, Ohio, South Dakota, Vermont, Washington, and Wyoming.

There isn’t much of a pattern to the list. Some states are traditionally Democratic, others traditionally Republican. Six of the states spend more on school operations per pupil than the national average. The other seven states spend less than the national average (per-pupil expenditure in Idaho, for example, is close to North Carolina’s PPE).

You’ll notice that Virginia dropped from the high performers when the focus shifted to disadvantaged students. It only exceeded the national average in science. No Southern states beat the spread in all three subjects. The region looked a little better when I threw in the four “honorable mention” states that exceeded the national average in two subjects: Colorado, Kentucky, Nebraska, and Texas.

North Carolina’s strongest subject is math, where our lower-income students did perform better than average. Indeed, the state’s overall performance in math has continued to improve over time while our reading performance has leveled off.

When the subject changes from how North Carolina fares in national rankings to how best to improve North Carolina’s performance, consensus disappears. I believe that the best-available empirical evidence recommends a strategy that includes strengthening testing and accountability measures, retaining and paying teachers according to performance, devolving additional authority and responsibly to local districts and schools, and fostering greater parental choice and competition in education.

That’s the strategy state lawmakers and the McCrory administration pursued during the 2013 legislative session. Teacher unions and liberal editorial pages screamed bloody murder about it, which should be treated as a useful indicator that progress was made.

Hood is president of the John Locke Foundation.