As a ninth-grader， Shanghai’s Li Sixin spent more than three hours on homework a night and took tutorials in math， physics and chemistry on the weekends. When she was tapped to take an exam last year given to half a million students around the world， Li breezed through it.
"I felt the test was just easy， " said Li， who was a student at Shanghai Wenlai Middle School at the time and now attends high school. "The science part was harder... but I can handle that."
Those long hours focused on schoolwork _ and a heavy emphasis on test-taking skills _ help explain why young students like Li in China’s financial hub once again dominated an international test to 15-year-olds called the Program for International Student Assessment， or PISA.