Anne Matsuura can easily recall her least favorite moment at Arlington's Yorktown High School last year. It was a day last fall when Yorktown's varsity tennis team suffered an agonizing defeat to the tennis team at archrival Langley High School in Fairfax County.

"This year we had our best chance," said Matsuura, explaining that Yorktown's tennis team had lost to Langley for several years in a row. "We were all psyched up to beat Langley. And then we lost very badly. It was a very, very sad day."

As much as she hates to lose, Matsuura believes that learning to take loss in stride is vital.

"You can't let it bog you down," she said. "You have to bounce back. Once you start getting down on yourself, then everything goes horribly."

The concept is difficult to imagine with Matsuura, who, along with 139 other American high school seniors, has been chosen this year as a Presidential Scholar. Matsuura was the only student from Northern Virginia to receive the honor.

The award, established by President Johnson in 1964 to promote excellence in education, goes to students who, among other things, have excelled on college entrance examinations, achieved an outstanding grade point average and demonstrated leadership potential.

Last semester, Matsuura juggled four advanced placement classes, Latin III and a college mathematics course at the Arlington Career Center, and was editor in chief of the school's first foreign language newspaper. On Monday, she graduated first in Yorktown's senior class, an unusually talented group, school officials say. Fifteen students were National Merit finalists and one-third of the 300-member class received the Presidential Academic Fitness Award, an honor given to seniors who maintained a B+ average or better.

"Most schools seldom get a Presidential Scholar," said Principal Steve Kurcis. "She's fabulous. She's serious-minded, has her head on her shoulders . . . . She has a real sense of determination."

"She's aggressive," said Anne Beasley, who has coached Matsuura in tennis for several years and considers her a very good player. "She has potential to play on a college team."

Matsuura said tennis has taught her about perseverance.

"Just because you play badly in one set doesn't mean you're going to lose," she said.

Matsuura, who has played for several years in tournaments in the mid-Atlantic division of the U.S. Tennis Association, said tournament playing builds "mental toughness."

Although her teachers and coaches are impressed with her determination, drive and achievement, they are equally impressed with the flip side: her calm, patience and ability to handle success.

"She's not just high achieving and doesn't give up; the neatest thing is that she also possesses the balance," Kurcis said. "She still can be social, friendly and have fun. She's fun to be around."

"She keeps a very good perspective on things," Beasley said. "She's been great for the other kids there. She's a role model."

If she can't come up with a math answer right away, "she takes a deep breath and says, 'Let's look at it this way,' " said Yorktown math teacher Donald Buttermore. "That takes a certain maturity."

Matsuura named Buttermore as the high school teacher who has had the most influence on her academic career.

Buttermore began working with Matsuura when she was in the fifth grade at Tuckahoe Elementary School. Gifted in math, Matsuura had been chosen as one of about a dozen Arlington elementary school pupils to work with Buttermore on spring afternoons on advanced math concepts.

"She was so intense and serious," said Buttermore, who described Matsuura as a "very, very strong" math student. "She would hang on every word you said."

Since elementary school, Matsuura has thought of Buttermore as a mentor, someone whose office she can stroll into to discuss math ideas. As a senior, Matsuura was Buttermore's aide, available to tutor other students in math.

"He's made math fun," remarked Matsuura, who said she has always found math satisfying: "You start out with a problem, you have to analyze it and you come out with a concrete answer."

Matsuura's fondness for that process has affected the kind of music she likes, according to her piano teacher of eight years.

"Because of the kind of mind she has, she's a Bach player," said Charlotte Shear, who described Bach compositions as "mathematical" and "thinking music."

Shear said she was surprised when she learned that Matsuura had been chosen as a Presidential Scholar, only because Matsuura never indicated that she had so many other involvements.

"She's very modest," Shear said.

Matsuura plans to attend Vanderbilt University in Nashville, where she has a four-year scholarship, and wants to go into medical research after she graduates.