Michael Wattendorf, president of the Black Student Union at Thomas Jefferson High School for Science and Technology in Alexandria. (Nikki Kahn/THE WASHINGTON POST)

Michael Wattendorf, a senior at Northern Virginia’s super-selective Thomas Jefferson High School for Science and Technology, stood before prospective members of its Black Student Union in the fall and introduced himself as the club’s president. The freshmen, Wattendorf recalled, looked a little confused.

“Yes,” Wattendorf remembers saying with a cheerful smile, “I am white.”

TJ, as the prestigious magnet school is known, has long struggled to boost its African American and Hispanic enrollment. Of the 1,800 students who attended TJ last year, only 34 were black and 42 were Hispanic, school figures show. The overwhelming majority of their classmates were Asian (906) and white (787).

To some, a white student at the helm of a club for black kids is a symptom of the school’s lack of diversity.

“If you have a black-student union and the person who is over it is white . . . what does that say? The pool [of black students] is not that large there,” said Charisse Glassman, who chairs the Fairfax County NAACP’s education committee and has met with TJ officials to discuss ways to increase minority enrollment. “A white person cannot understand what black children are going though when they go to that school.”

To others, Wattendorf’s presidency is a symbol of something more high-minded about the school: Its black students were willing to look beyond race.

“It’s a great reflection on the people who voted for me. They didn’t let race be a factor in their voting — they voted on the merits of my ideas,” said Wattendorf, 17, who spearheaded a mentoring program for elementary schools in Fairfax with high minority populations and just won the Princeton Prize in Race Relations.

The prize, given to more than two dozen high-schoolers nationwide by Princeton’s local alumni committees, recognizes efforts by young people to improve racial harmony and carries with it a $1,000 award. Wattendorf said he plans to give the money to his club, which has about 15 members who show up regularly.

For Howard Small, a 17-year-old African American junior who is a member of the club, Wattendorf’s victory was initially jarring.

“It was weird and difficult to accept. We’ve had other white members and [non-blacks], but having a white person as a our leader? I didn’t know how to feel about it,” said Small, who did not vote for Wattendorf.

But Small said he has come around. It was Wattendorf’s idea, Small said, to invite the elementary-schoolers in the mentoring program to the school’s talent show. And the club’s new leader has missed meetings only for college visits.

“He’s been really good as president,” Small said. “We’re all okay with it now.”

Chantelle Ekanem, 17, a black senior and a former Black Student Union president who also ran for club president in the most recent election, said that after Wattendorf was elected, one of her girlfriends cracked a joke about him being white.

“It was an honest reaction,” Ekanem said. “People were just like, ‘That’s kind of odd.’ ”

But Ekanem said Wattendorf is devoted to the club and to increasing diversity at their school.

“Michael took a big part” in developing the program for elementary schools, she said. “I’m glad he’s president. He cares a lot about the program.”

Wattendorf joined the Black Student Union as a sophomore. A white cross-country teammate who was already in the Black Student Union showed him some step dance moves that were part of the club’s upcoming talent show act. Wattendorf got hooked and performed in the show.

His interest in the club grew more serious when he was asked to speak to counselors from Fairfax middle schools with low TJ acceptance rates. He did not sense that they were excited about TJ or that they were going to encourage their students to apply.

“I think the admission of a diverse population will come if you have a diverse population applying,” Wattendorf said.

Then, after reading a Washington Post article about TJ’s continuing dearth of black and Hispanic students, Wattendorf and other club members hatched an idea to launch a mentorship program for three high-minority elementary schools that do not typically send large numbers of students to TJ: Franconia, Rose Hill and Springfield Estates.

By the end of his junior year, Wattendorf — who is weighing admissions offers from Princeton, Harvard and the University of Virginia — decided to run for club president. It was not until after he had won that he told his parents about his new position.

“I don’t remember it being that big of a deal,” said his father, Daniel Wattendorf, 42, a geneticist at the Defense Advanced Research Projects Agency.

Alexandria Sutton, an African American club member who also ran, said her relatives and friends were taken aback that she had lost.

“They were more like, ‘Really? How is that possible?’ ” recalled Sutton, 17, who is considering going to Spelman College, a prestigious, historically black college for women in Atlanta, next year. “I don’t think they realized that a non-black person was so invested in the club to be president.”

She has no problem with Wattendorf leading the group. To her, he could help lure more members and make the club even stronger. After all, many civil rights and minority advocacy groups have long included white members.

“People would realize you don’t have to be black to join,” she said. “But the fact that there are so few minorities at TJ to begin with, it does make sense that there could be a white president.”

The demographic disparities at TJ exist at other highly selective magnet schools around the country. At Stuyvesant High School in New York, for example, there are only 40 black and 80 Hispanic students out of nearly 3,300, according to the school’s figures.

Evan Glazer, TJ’s principal, said the school is doing all it can to increase African American and Hispanic enrollment, including expanding its outreach and mentoring programs at elementary and middle schools across Fairfax that do not feed large numbers of students into TJ.

Despite their small numbers, black students seem comfortable at TJ, said Haywood Torrence, an African American government teacher who is the Black Student Union’s sponsor. Only occasionally, he said, does he hear complaints about racial slights or tensions.

“Some of [the black students] have described to me things that have made them feel as if perhaps some of their peers did not feel they fully belong here,” said Torrence, who was one of the first blacks in the 1960s to integrate his own high school in southern Virginia before graduating from the Phillips Exeter Academy and Harvard.

Sometimes in their weekly meetings, the club members tackle complex issues that deal with race and cultivate nuanced opinions about often-murky events. At one recent meeting, talk turned to the case of Florida 17-year-old Trayvon Martin, who was shot and killed in February by George Zimmerman, a neighborhood crime-watch volunteer. Zimmerman says he acted in self-defense.

“I think it’s really sad that people are trying to discredit Trayvon Martin’s name,” Marcus Prater, 17, an African American junior, told the club. “People are saying he was a bad kid and it was coming his way, but there’s no impromptu homicide that was warranted.”

Seated at the front of the classroom, Wattendorf sounded a note of caution.

“I understand what you’re saying,” he said. “But to offer the alternative opinion . . . if there was a chance he was beating Zimmerman, that is important to know.”

After the meeting, Prater said in an interview that Wattendorf is not always going to share the same perspective as the African American members of the club.

“He’s done an amazing job as president. He was the best person who ran,” Prater said. “But I don’t think he understands that Trayvon Martin could have been me. I think Michael knows [the case] is awful, but when you feel like you could be in the same shoes, that you could die and people would defend your killer, well, you have a completely different viewpoint.”