A couple of years ago, Majur Juac took time from his job as a security guard in suburban Washington to come to New York for a visit.

The soft-spoken Sudan native dropped by a chess tournament in Forest Hills, Queens, that a friend was competing in. He was encouraged to play as well.

“He won it,” said Michael Propper, the co-director of New York City Chess Inc., the organization that sponsored the tournament.

New York City Chess teaches the game to 6,000 students every year in private and public schools, chess camps and other events.

“I asked him if he ever taught chess. I gave him my card,” Mr. Propper recalled. “The next day he came in with his certificate to show us he’s a national master.”