A Whiz Manages to Find Time to Be a Kid : L.A. County: Kevin Armstrong, 17, the leading scorer in his decathlon, could have gone to college at 13. But he didn’t want to miss the fun of growing up.

The highest-scoring student in the Los Angeles County Academic Decathlon could have enrolled in college when he was 13, but he would have missed some of his favorite high school pastimes--such as being towed behind a car on a cafeteria tray.

Geniuses, especially teen-age ones, need to let off steam.

So that’s what Kevin Armstrong, 17, and some other members of the William S. Hart High School team from Santa Clarita did in November after the grueling, daylong academic decathlon. They “land-surfed” on towed plastic trays in a parking lot, crashed a girls’ slumber party and rode boogie boards down the slopes of a golf course.

Armstrong arrived home after the test at 4 a.m. to a stern lecture from his worried parents. But the slim, brown-haired youth emerged from the doghouse and into the limelight when county education officials announced Nov. 26 that he had earned 8,616 points--of a possible 10,000--in the decathlon, beating 637 other competitors from 64 other schools.

His strong showing boosted the Hart team into second place.

Draped for a photo session with the nine gold, silver and bronze medals he earned in the competition, Armstrong said he chose not to enroll in a program for gifted children at Cal State Los Angeles when he was 13 because he wanted to participate in high school activities.

“Studying isn’t the only thing in life,” Armstrong said. “I wanted to have a broader life and experience the people around me.”

As for the high jinks after the test, he said, “I generally don’t blow it that much.” Most of the time, Armstrong “enjoys” calculus, works as a clerk in a marble-fixture factory after school and trains for the track and field team, he said.

“Like any teen-ager, he has his off moments, but 99% of the time he behaves,” said Craig Armstrong, Kevin’s father, an executive for a hotel chain.

Last year, Armstrong scored 7,065 points in the decathlon. The top scorer was another Hart student and friend of Armstrong, Jon Sorenson, who earned 8,255 points.

With two top scorers in a row, “Hart has really shown genuine progress,” said Ann Bradley of the Los Angeles County Office of Education.

Armstrong was determined this year to better the score achieved by his friend, Sorenson, who is now in college. So, he practiced with teammates, arriving at school at 7 a.m. for an hour drill, and studying at night.

“Kevin wants to be top dog in certain things,” his father said. “That’s just the way he is.”

The hard work paid off when Armstrong topped his previous score by 1,551 points, beating Sorenson’s score by 361 points.

The test is divided into 10 sections, including science, math, an interview with the judges and a written essay. The theme this year was “Habitat Earth: Ecology and the Environment.”

Armstrong is a “renaissance student” who did well in all 10 sections of the test, said Dick Sholseth, coordinator of the county’s decathlon. But he excelled in math and science.

“I’ve always been interested in little gizmos, in everything that moved or flew or swam,” said Armstrong, who may study engineering in college. “If you like everything, like I do, it’s really tough to decide on a career.”