America's child poverty problem does not entirely explain away its students' relatively low math scores, says a report from Harvard's Program on Education Policy and Governance.

Researchers analyzed scores from the International Program for International Student Assessment (PISA) test, which is given in 65 countries.

In 2009, about 32 percent of American students scored what the researchers termed "proficient" on the PISA, which placed it 32 out of 65 countries. Fifty percent or more of students in Korea, Finland, Switzerland, Japan, Canada and the Netherlands scored proficient.

Previous studies have suggested that Americans out-score other countries once you control for poverty. A U.S. Department of Education report found that American kids in schools where less than 10 percent of the students received free or reduced lunches, a measure of poverty, outperformed all other countries' kids on the reading portion of the PISA test. Schools with 25 percent or fewer kids in poverty lagged behind only Norway and Korea.

But the Harvard researchers, using different measures, found that poverty did not seem as big of a factor in how Americans scored on math. When the researchers just looked at students with at least one college-educated parent, a good indicator that the child is above the poverty line, only 44.4 percent were proficient in math, trailing significantly behind students in 13 countries.

Using another common metric of poverty, race, American students still lagged behind. Only 41 percent of white students scored proficient on math. (About 10 percent of white children live in poverty, much lower than the overall rate.) Meanwhile, 11 percent of black students and 15 percent of Hispanic students scored proficient on math.

The 2009 PISA scores, released last December, delivered the depressing news that even though American students live in the richest country in the world, they trail, on average, significantly behind their neighbors in math skills. Education Secretary Arne Duncan called the scores a "wake up call for America" and a reason to continue the Obama administration reforms linking teacher evaluations to students' test scores.

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But others, like education historian and teachers' union defender Diane Ravitch, said the scores were a reflection of the larger problem of child poverty, which can't be fixed by education reforms alone. She writes in an email to The Lookout that she still believes achievement is "tightly correlated with family income," despite the new analysis.

She points out that the U.S. has a 20 percent child poverty level. "That's the crisis, not test scores," she writes.

The report also brushes away the argument that math performance doesn't matter, as U.S. students trailed the competition 50 years ago but our economy has boomed ever since. The researchers argue that boosting U.S. kids' math scores to the level of South Korea would result in a 1.3 percentage jump in GDP each year, totaling $75 trillion over 80 years.