Most results come from a sampling of scores from countries as a whole, but in China it was given in select regions.

The U.S. Education Department's National Center for Education Statistics released the results. The test, given every three years to 15-year-olds, is designed to assess students' problem-solving skills.

U.S. scores on the PISA haven't changed much since testing started in 2000, even as students in countries like Ireland and Poland have shown improvement and surpassed U.S. students.

Irish Education Minister Ruairi Quinn said the results reflected improvements among Ireland's lower-achieving students, even as the country's top students underperformed compared to those in other countries.

"While these are only one set of test results at one point in time, I am delighted to see Irish students performing well in reading and science and quite well in mathematics," he said.

In Britain, scores were about the same as three years ago, prompting debate about why the country has not improved despite increased spending on education. The nation did better than the United States in math and science but was not among the top performers in any subject.

"Since the 1990s, our performance in these league tables has been at best stagnant, at worst declining," said Britain's Education Secretary Michael Gove, adding that the results "underline the urgent need for our reforms."

Gove's ruling Conservative Party and the opposition Labour Party both blamed each other's policies for the results.

Meanwhile a business organization said Britain has fallen behind in part because of "historic complacency" and a lack of focus on achievements and results compared to Asian countries.

"Countries with an unrelenting focus on the quality and rigor of their education system will be the ones who win," said Mike Harris at the Institute of Directors.

Tom Loveless, a senior fellow at the Brookings Institution, cautions about reading too much into the results from Shanghai, which also dominated the test in 2009. The students tested are children of the elite. They are the ones allowed to attend municipal schools because of restrictions such as those that keep many migrant children out, he said.

"The Shanghai scores frankly to me are difficult to interpret," Loveless said. "They are almost meaningless."

But Jack Buckley, commissioner of the National Center for Education Statistics, said U.S. officials have not seen any evidence of a "biased sample" of students tested in Shanghai. If the entire nation was included, he said it's unclear what the results would show.

Marc Tucker, president of the National Center on Education and the Economy, said Shanghai has worked hard to bring migrant children into its schools and has put an emphasis on improving teacher quality — a factor helping to drive its test scores.

In the education community, Finland has drawn notice for its past test performance, but this year its average PISA score dropped in all three subjects, most pronounced in math. Finland's students did better on average than those from the United States.

Overall, National Education Association President Dennis Van Roekel said among the Asian nations dominating the test, "The one thing they all have in common is that they make a real commitment to education for all kids, and nothing deters them from that vision, and then they do what's necessary to make that happen. In the United States, we don't have the commitment for all kids and it needs to change."

The test is based on a 1,000-point scale. Among the findings:

— In math, average scores ranged from 368 in Peru to 613 in Shanghai. The international average was 494.

— In science, average scores ranged from 373 in Peru to 580 in Shanghai. The international average was 501.

— In reading, average scores ranged from 384 in Peru to 570 in Shanghai. The international average was 496.

_____

Associated Press writers Greg Katz and Sylvia Hui in London contributed to this report.

_____

Online:

.