Almost everyone who worries about America's "competitiveness" in the world bemoans the sorry state of U.S. K-12 education. The Chinese and others do better. We need to catch up. From President Obama to CEOs, the refrain is to "fix the schools," almost as if it were an engineering problem. "The urgency for reform has never been greater," Education Secretary Arne Duncan recently wrote in The Post. The diagnosis spans the political spectrum. But what if it's not true?

There are grounds for doubt. For starters, economic competitiveness depends on more than good schools, which are important but not decisive. To take an obvious example: The Japanese have high test scores, but Japan's economy languishes. Its export-led growth has foundered. Next - and as important - American schools are better than they're commonly portrayed. We now have a massive study of the reading abilities of 15-year-olds (roughly 10th-graders) in 65 systems worldwide showing that U.S. schools compare favorably with their foreign counterparts.

The most pessimistic view of the study is that, on average, American schools do as good a job as schools in other wealthy nations. We're worse than some and better than others. The overall loss of economic competitiveness is likely modest and would be swamped by other factors (government policies, business management, exchange rates, the willingness to take risks). But a more detailed evaluation of the study - comparing similar students in different countries - suggests that U.S. schools still rank high in the world.

The study, called the Program for International Student Assessment (PISA), was conducted by the Organization for Economic Cooperation and Development in Paris. It covered the OECD's 34 mostly wealthy member nations (including the United States, most European countries and Japan) and 31 others. The test was scored on a zero to 1,000 scale, and the best-performing students were in Shanghai, China, (one testing area that's not a country), with an average score of 556. South Korea (539) and Finland (536) were next. The United States ranked 17th (500), slightly above the average (493) of the OECD's advanced countries. This was behind Japan (520) and Belgium(506), and just ahead of Germany (497), France (496) and Britain(494).

Good, perhaps. But not great.

However, the overall scores don't tell the full story. The U.S. Education Department examined the American scores by race and ethnicity. This report ("Highlights from PISA 2009") allows comparison with countries whose ethnic and racial compositions are more homogeneous than ours. For example, you can compare the scores of white non-Hispanic Americans with the scores from Canada, a country that is almost 85 percent white. This is an admittedly crude approach, but it suggests that U.S. schools do about as well as the best systems elsewhere in educating similar students.

Among non-Hispanic white Americans, the average score was 525 - not very different from Canada's 524, New Zealand's 521 or Australia's 515. All these countries are heavily white, and all ranked in the top 10 of the 65 participating school systems. The story is the same for Asian Americans. Their average score was 541 - somewhat below Shanghai, about even with South Korea and ahead of Hong Kong (533) and Japan. Again, all these other systems were in the top 10.

American schools are hardly perfect. Math scores, though showing the same pattern, are lower than reading scores. We can learn from other countries better ways to teach math. But the most glaring gap is well-known: the stubbornly low test scores of blacks and Hispanics. In the PISA study, their reading scores were 441 (blacks) and 466 (Hispanics). Changing this is the great challenge for schools, because the share of black and Hispanic students is growing. It was 23 percent in 1980, 35 percent in 2009.

Americans have an extravagant faith in the ability of education to solve all manner of social problems. In our mind's eye, schools are engines of progress that create opportunity and foster upward mobility. To the contrary, these persistent achievement gaps demonstrate the limits of schools to compensate for problems outside the classroom - broken homes, street violence, indifference to education - that discourage learning and inhibit teaching. As child-psychologist Jerome Kagan points out, a strong predictor of children's school success is the educational attainment of their parents. The higher it is, the more parents read to them, inform and encourage them.

For half a century, successive waves of "school reform" have made only modest headway against these obstacles. It's an open question whether the present "reform" agenda, with its emphasis on teacher accountability, will do better. What we face is not an engineering problem; it's overcoming the legacy of history and culture. The outcome may affect our economic competitiveness less than our success at creating a just society.