Critics argue that Chinese teachers place an unhealthy emphasis on test preparation and rote memorization at the expense of critical thinking skills and creativity. They also say international exams overstate the strength of China’s system because they exclude students from poorer regions.

The Stanford study, based in part on exams given to 2,700 students at 11 mainland universities, has its own limitations. It does not account for people who are not enrolled in universities, a large swath of Chinese youth. It looks exclusively at students in computer science and engineering programs. And while it measures critical thinking, it does not offer insight into creativity, a topic often hotly debated in discussing the Chinese education system.

Still, the researchers found stark differences when they compared Chinese students with their overseas counterparts.

In addition to examining critical thinking skills, the study looked at how Chinese students compared in math and physics. While testing for the United States is not yet available, the researchers found that Chinese students arrived at college with skills far superior to their Russian counterparts.

After two years of college, though, the Chinese students showed virtually no improvement while the Russians made substantial progress, though not enough to catch up.

The Stanford researchers suspect the poor quality of teaching at many Chinese universities is one of the most important factors in the results. Chinese universities tend to reward professors for achievements in research, not their teaching abilities. In addition, almost all students graduate within four years, according to official statistics, reducing the incentive to work hard.

“They don’t really flunk anyone,” said Scott Rozelle, an economist who has studied Chinese education for three decades and a co-author of the study. “The contract is, if you got in here, you get out.”