(CNN) When it comes to science, math and reading, Singapore's teens are the best in the world, according to a international education survey published Tuesday.

In all three subjects, Singapore students demonstrated knowledge and skills equivalent to almost two additional years of schooling compared to students in the US, France and Sweden.

The US improved on its 2012 performance by moving up to 25 on the list.

The findings are part of the 2015 Program International Student Assessment (or PISA) -- a benchmark of education systems conducted every three years by the Organization for Economic Cooperation and Development (OECD), a grouping of the world's richest economies.

More than half a million 15-year-olds in 72 countries and economies sat a two-hour exam last year. This time around, science was the main focus compared with math in 2012.

China slips

East Asia performed best overall, occupying seven of the top spots for science. Estonia, Finland and Canada were the top ranking non-Asian countries.

Singapore, long considered an educational powerhouse, ranked first in science, math and reading. China slipped to 10th place after coming top in 2009 and 2012.

The country was represented by students from four regions -- Beijing, Jiangsu, Guangdong and Shanghai. In previous assessments only teens from the wealthy city of Shanghai were tested and many had questioned to what extent the city's success was exceptional.

"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.

US, UK middling

The United States ranked 25th in the league table, performing in line with the OECD average for science and reading -- but below average for math. Students in Massachusetts and North Carolina took part in the assessment.

Students in the UK did slightly better, coming 15th, above the OECD average for science and reading and in line with the average for math.

Both countries improved on their 2012 performance , when they ranked 36th and 26th.

Top 10 for reading Singapore (535)

Canada/ Hong Kong (527)

Finland (526)

Ireland (521)

Estonia (519)

Korea (517)

Japan (516)

Norway (513)

New Zealand//Germany/Macau (509)

Schleicher, the OECD's director of education, said that despite their lower scores American students were more science-minded than some of their Asian counterparts.

"They report more frequently than Chinese students do that they value scientific approaches to enquiry, adopt a questioning approach, search for data and their meaning, demand verification, and respect logic and pay attention to premises," Schleicher said to CNN.

"This is important. Education used to be about teaching people facts and theorems; now, it's about helping students develop a reliable compass and the navigation skills to find their own way through an increasingly uncertain, volatile and ambiguous world."

"While East Asian students score higher in science, they need to develop more positive attitudes towards science," Schleicher said.

The report also asked students how long they spent studying -- both at home and school -- and it didn't necessarily correlate with performance.

Students in China said they spent close to 57 hours per week studying in school or at home; compared to 36 hours for students in high-performing Finland.

The data also showed that the world is no longer divided between rich and well-educated nations and poor and badly-educated ones.

For example, 10% of the most disadvantaged students in Vietnam stacked up favorably to the average student in the OECD's 35 member countries, the report said.

Gender attitudes

The report also looked at gender attitudes toward science.

On average, the report found, boys and girls are almost equally likely to expect to work in a science-related field. Some 25% of boys and 24% of girls expect to be working in a science-related occupation when they are 30.

Top 10 for maths Singapore (564)

Hong Kong (548)

Macau (544)

Taiwan (542)

Japan (532)

China (531)

Korea (524)

Switzerland (521)

Estonia (520)

Canada (516)

However, boys and girls seem to be interested in different areas of science, with boys more interested than girls in physics and chemistry, while girls tend to be more interested in health-related topics.

Boys score four points higher than girls in science, on average across OECD countries -- a small, but statistically significant difference.

They perform much better than girls in 24 places, with the largest gap found in Austria, Costa Rica and Italy, where the difference between boys' and girls' scores is over 15 points.

Gender-related differences towards science appear more related to disparities in what boys and girls think they are good at and is good for them, than to differences in what they actually can do, the report said.

"Stereotypes about scientists and about work in science-related occupations (computer science is a "masculine" field and biology a "feminine" field; scientists achieve success due to brilliance rather than hard work; scientists are "mad") can discourage some students from engaging further with science," the report said.

By contrast, PISA has found that girls consistently outstrip boys in reading, with girls outperforming by 27 points on average, but that gender gap is narrowing.

Between 2009 and 2015, the gender gap in reading narrowed by 12 points on average across the 35 OECD countries.

In math, boys outperformed girls by eight points, with the difference largest in Austria, Brazil, Argentina, Chile, Costa Rica, Germany, Ireland, Italy, Lebanon and Spain.