LOS ANGELES (AP) — More than 104,000 students worldwide took the Advanced Placement Calculus exam this year. Only 11 got a perfect score. California 17-year-old Nathan Chou is one of them.

The Arcadia High School senior learned of the rare achievement from the College Board, the nonprofit group that oversees the AP tests.

Chou told the Los Angeles Times in a story Sunday that he spent about four hours studying for the calculus exam, with help from class-made study guides and practice tests.

"That was helpful," Nathan said. "But I almost ran out of time on the multiple-choice section. I was nervous that my memory would suddenly blank out."

The test was offered in 59 countries in the 2012-2013 school year. The 11 students who earned perfect scores are all from the United States. At least two other students in California earned perfect scores on the exam, said Deborah Davis, the board's director of college readiness communications.

Nathan took the test previously as a junior. He said the concepts were easy to understand but applying them to calculus problems was challenging.

Nathan has maintained straight A's in high school and plays the violin and piano in the school's symphony orchestra.

His father told the newspaper the family will visit one of Nathan's favorite restaurants to celebrate the accomplishment.

___