students
Students arrive to receive their GCSE results at Stoke Newington School on Aug. 20, 2015 in London, United Kingdom. Dan Kitwood/Getty Images

The United States still lags behind many countries in education, according the latest results from the Programme for International Student Assessment published Tuesday. Students in Singapore, meanwhile, were the best-performing in the world.

The tests are a benchmark exam carried out every three years by the Organization for Economic Cooperation and Development, a group that brings together some of the richest countries in the world. The exams test 15 year olds in 70 countries across the globe to assess students' education levels.

On average, U.S. students were middling in every subject tested: science, math and reading. Out of 1,000 points total the U.S. scored 496 in science, which narrowly outpaced the OECD average of 493. In math the U.S. average was 470, well below the OECD average of 490 points. U.S. students averaged a score of 497 in reading, outpacing the OECD average of 493. Of the 35 OECD countries, U.S. ranked 19th in science, 31st in mathematics and 20th in reading.

Singapore, meanwhile, topped each subject the exams tested. Its students averaged a score of 556 in science, 564 in math and 535 in reading.

"U.S. students are running in place" in science and reading, U.S. Secretary of Education John King Jr said in a statement, via the Los Angeles Times. "We’re losing ground."

Canada, Estonia, Finland and Japan all did well on the tests, while China's performance slipped a bit, especially in science, where it fell to tenth. The United Kingdom's results were somewhat average but better than those of the United States. Its students scored an average of 509 in science, 492 in math and 498 in reading.

In total, East Asian countries tested the best, which the OECD pegged as a product of attitude.

"The fact that students in most East Asian countries consistently believe that achievement is mainly a product of hard work, rather than inherited intelligence, suggests that education and its social context can make a difference in instilling values that foster success in education," said Andreas Schleicher, the OECD's director of education, according to CNN.