WASHINGTON (AP) — Results from a global exam given to 15-year-olds show U.S. students lagging in math and just average in science and reading, while teens from Asian nations dominate the categories.

Education Secretary Arne (AR'-nee) Duncan calls the results released today a "picture of educational stagnation."

U.S. students showed little improvement and failed to reach the top 20 in any of the three categories.

The top average scores in each subject came from Shanghai, China's largest city, with more than 20 million people. Singapore, South Korea, Japan, and Hong Kong were among the participants with students scoring at the top on average in each subject.

Duncan says the solution includes early education, higher academic standards, affordable college and the recruitment and retention of top-notch educators.

About half a million students in 65 nations and educational systems took part in tests last year.