Renee Dudley, Steve Stecklow, Alexandra Harney and Irene Jay Liu

Internal documents show that the U.S. college entrance exam has been compromised in Asia far more often than acknowledged. And the newly redesigned SAT retains a key vulnerability that the test-prep industry has exploited for years.

Xingyuan Ding is a sophomore at the University of California, Los Angeles, one of America’s most exclusive public universities. In applying to schools, the 20-year-old from China took the SAT college entrance exam four times.

He had an advantage on his final try: a booklet compiled by a Shanghai test-preparation school he attended.

His study aid was far more valuable than the practice questions that students in America use to prepare for the SAT, the standardized test used by thousands of U.S. colleges to help select applicants. Known in Chinese as a jijing, the booklet was essentially an answer key. It revealed words from the correct responses to multiple-choice questions that had appeared on past SATs – many of which would be used again on the exam Ding took.

Thanks to the booklet, Ding said he already knew the answers to about half of the critical reading section of the SAT when he took the test in Hong Kong in December 2013.

“I felt really lucky,” Ding said.

His score on that section? A perfect 800, he said.