It isn't easy to be a disadvantaged high school student anywhere, but the U.S. education system appears to be particularly unkind to its less privileged youth.

Poor students have a tougher time overcoming their socioeconomic odds in the U.S. than in Canada, France, Russia, and 33 other countries, according to a new global report by the OECD. Only about 20 percent of disadvantaged students in the U.S.—those in the bottom 25th percentile of the PISA index of economic, social and cultural status— show academic performance that's in the top 25th percentile internationally. In Russia and France, that percentage is only slightly higher; in Canada it's nearer to 35 percent. In a handful of East Asian countries, including Singapore, Vietnam, and several provinces in China, well over 60 percent of disadvantaged students rank in the top quarter of international students. The average among all OECD member countries is roughly 25 percent.

It's hardly the first measure by which the U.S. education system has gravely disappointed. Last year, a similar report concluded that American adults performed worse in math, reading and technology-driven problem-solving than nearly every other country in the group of developed nations. And recent testing results have shown little to no improvement.

But the lackluster performance among America's underprivileged youth should be particularly troublesome. Not only is it an injustice to the growing number of low-income students entering the country's education system, it's also a disservice to the economic well-being of the U.S. at large. Inequity in education is both socially and financially irresponsible. Even a marginal improvement in the mathematics performance of 15-year-olds, the OECD report finds, would lead to more than $200 trillion in added economic output over the course of their working lives.