(CNN) Teens from some of China's wealthiest regions are outperforming their peers in the world's richest countries in reading, math and science, according to new results from a global education study.

The survey found that 15-year-old students from Beijing, Shanghai, and the eastern provinces of Jiangsu and Zhejiang ranked top for all three core subjects, achieving the highest level 4 rating.

Students from the United States were ranked level 3 for reading and science, and level 2 for math, while teens from Britain scored a level 3 ranking in all three categories.

The findings are part of the 2018 Program International Student Assessment (PISA) -- a global yardstick of education systems taken every three years by the Organization for Economic Cooperation and Development (OECD), a grouping of the world's richest economies.

Impressive performance

China's success in the survey is likely to come under question due to the fact that only four of the country's wealthiest areas were surveyed -- meaning that the results don't accurately represent the tens of millions of students living in other parts of the country, especially rural areas.

In 2012, PISA's results were heavily criticized for only including students in Shanghai as the sole representative of mainland China, a country of more than a billion people.

The next survey in 2015 was broadened to include four provinces and cities -- Shanghai, Beijing, Jiangsu and Guangdong. China still performed well that year , but its scores were down across the board compared to the previous survey, when only Shanghai students were surveyed.

The Shanghai exam results have previously come under fire for shutting out the city's migrant children and not being representative of the city's total student population, which the OECD denies

Angel Gurria, the secretary-general of the OECD, said in the latest report's preface that the performance of the four Chinese regions was impressive, as their income levels were below the OECD average.

"These four provinces/municipalities in eastern China are far from representing China as a whole, but the size of each of them compares to that of a typical OECD country, and their combined populations amount to over 180 million," he said.

"The quality of their schools today will feed into the strength of their economies tomorrow."

In OECD nations, the average household net adjusted disposable income per capita is around $30,500, per the most recent figures available on the organization's Better Life Index

That's more than three times the highest equivalent levels in China. In 2018, Shanghai residents had the largest average disposable income in the country at $9,100, state-run newspaper China Daily reported in March, citing the National Bureau of Statistics.

Not a competition

A record 600,000 students across 79 different countries and territories sat the 2-hour PISA test last year, the OECD said.

The report's authors stressed that the goal was not to pit countries against each other in competition, but rather to "provide useful information to educators and policy makers concerning the strengths and weaknesses of their country's education system."

"When ranking countries, economies and education systems in PISA, it is important to consider the social and economic context in which education takes place," the report found.

core The survey also warned of some troubling trends shown by thecore 36 OECD countries.

In the past decade, those nations increased their expenditure on education by a rate of more than 15% per primary and secondary school student, according to the survey's authors. But most of the countries saw virtually no improvement in the performance of their students since PISA was first conducted in 2000.

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Smartphones and disinformation

The authors of the report said critical thinking and reading comprehension are particularly important in the smartphone era, so students can learn how to weed out the truth from fiction.

"In the past, students could find clear and singular answers to their questions in carefully curated and government-approved textbooks, and they could trust those answers to be true. Today, they will find hundreds of thousands of answers to their questions online, and it is up to them to figure out what is true and what is false, what is right and what is wrong," the report said.

"Reading is no longer mainly about extracting information; it is about constructing knowledge, thinking critically and making well-founded judgements."

Fewer than one in 10 students surveyed in the OECD countries could "distinguish between fact and opinion, based on implicit cues pertaining to the content or source of the information," the report said.

The only areas in which more than one in seven students demonstrated the ability to distinguish fact from opinion were the four parts of China, Canada, Estonia, Finland, Singapore and the United States.