U.S. students are continuing to trail behind their peers in a pack of higher performing nations, according to results from a key international assessment.

Scores from the 2009 Programme for International Student Assessment to be released Tuesday show 15-year-old students in the U.S. performing about average in reading and science, and below average in math. Out of 34 countries, the U.S. ranked 14th in reading, 17th in science and 25th in math.

Those scores are all higher than those from 2003 and 2006, but far behind the highest scoring countries, including South Korea, Finland and Singapore, Hong Kong and Shanghai in China and Canada.

“This is an absolute wake-up call for America,” U.S. Education Secretary Arne Duncan said in an interview with The Associated Press. “The results are extraordinarily challenging to us and we have to deal with the brutal truth. We have to get much more serious about investing in education.”

The PISA exam is one of a handful of tests that compare educational levels across nations, and is considered to be the most comprehensive. The test focuses on how well students are able to apply their knowledge in math, reading and science to real-life situations. Some 470,000 students took the test in 2009 in 65 countries and educational systems, from poor, underdeveloped nations to the most wealthy.

Student performance on international assessments is considered especially relevant as today’s high school graduates enter a global job market, where highly skilled workers are in increasing demand.

The United States’ mediocre scores on the PISA exam have repeatedly been highlighted by the Obama administration and others pushing for education reform. A number of countries have made significant improvements in recent years, while the U.S. has made only incremental advancements.

Between 1995 and 2008, for example, the United States slipped from ranking second in college graduation rates to 13th, according to the Organisation for Economic Co-operation and Development, the Paris-based organization that develops and administers the PISA exam. Of 34 OECD countries, only 8 have a lower high school graduation rate.

Responding to the grim figures, President Barack Obama has set a goal for the U.S. to have the highest proportion of students graduating from college in 2020.

“We live in a globally competitive knowledge based economy, and our children today are at a competitive disadvantage with children from other countries,” Duncan said. “That is absolutely unfair to our children and that puts our country’s long term economic prosperity absolutely at risk.”

The impact of improving math, reading and science scores could be radical: A recent OECD study with Stanford University projected that if the U.S. boosted its average PISA scores by 25 points over the next 20 years, there would be a gain of $41 trillion in the U.S. economy over the lifetime of the generation born in 2010.

The 2009 exam had an extra focus on reading, and looked at how factors such as family background, equity of resources, and governance influence educational outcomes.

The top performers in reading were South Korea, Finland, Hong Kong and Shanghai in China, Singapore, Canada, New Zealand, Japan and Australia.

The gap between the highest performing countries and the United States is stark — students in Shanghai, for example, had an average score of 556 points in reading, 56 points higher than the 500-point average reached by United States students. Shanghai students also posted the highest score in math, with an average of 600 points, 113 points higher than the 487 point U.S. average.

OECD Secretary-General Angel Gurria cited ongoing evaluations, an emphasis on the importance of education, and a curriculum that is relevant to everyday life as reasons for the Chinese success.

“They don’t only produce children who know the matters by heart,” Gurria said. “They’re educated to understand and face the challenges of real life.”

He noted that the Chinese scores were strong in all three subject areas.

“That speaks about who is going to be leading tomorrow,” Gurria said.

The Shanghai and Hong Kong results are certainly unrepresentative of China as a whole — additional results from other regions will be release next year, but Andreas Schleicher, head of the Indicators and Analysis Division at the OECD said he didn’t expect much variation.

The report also notes that the GDP per capita in Shanghai is well below the OECD average — highlighting another finding of the study: Low national income does not necessarily signify poor educational performance. South Korea, another top performer, also has a GDP below the OECD average.

“While national income and educational achievement are still related, PISA shows that two countries with similar levels of prosperity can produce very different results,” Gurria said. “This shows that an image of a world divided neatly into rich and well-educated countries and poor and badly education countries is now out of date.”

The United States spends more per student, on average, than other countries. In the 2009 PISA study, only Luxembourg spent more per student. The report notes that countries like Estonia and Poland perform at about the same level as the United States, while spending less than half the amount per student.

“I think we have to invest in reform, not in the status quo,” Duncan said.

The PISA study does not look to draw cause-and-effect relationships, but does highlight some findings about what the top performing countries tend to have in common.

Schleicher noted that some of the top systems are centralized, while others are very decentralized. There was also much variation in class sizes, with some of the best performers finding success in putting quality teachers in larger classes. But in each case, teachers are subject to evaluations and have a high standing in society. Also, schools have a degree of autonomy in determining their curriculum — but are also held accountable.

“In other words, autonomy without accountability would be a very bad outcome,” he said.

He said many of the things the United States is doing, such as developing common academic standards and smarter assessment systems, are important, positive changes.

“What we have seen from other countries doing similar things is those initiatives do pay off in the longer term,” Schleicher said.

The study found that the best school systems were also the most equitable, meaning students from disadvantaged backgrounds were just as likely to do well academically. In the U.S., 17 percent of the variation in student performance was found to be related to a pupil’s background — compared to 9 percent, for example, in Canada.

The report notes that Canadian 15-year-olds, on average, perform more than one school year ahead in math than 15-year-olds in the United States, and more than a half year ahead in reading and science. Canada, like the U.S., has a decentralized education system.

“Canada’s experiences raise questions about why the United States has so far not equaled the performance of it northern neighbour,” the report states.

Mexico had the lowest reading score among OECD member countries, with an average of 425 points — the equivalent of more than two school years behind the highest member score. Among all 2009 participants, there was a gap of 242 points between the highest and lowest reading scores — equal to more than six years of schooling.

Mexico was commended for reducing the number of low performers in reading, and for improving math scores.

Gurria said the report’s overall message is that, “Even in this crisis and even with the expenditure cuts, keep on supporting the education but also look at what successful systems have in common. They all can be very different but they have in common a number of features that can really make for better systems.”