On a patch of turf on the sidelines of crowded athletic fields on Randalls Island, under the rattle of the Robert F. Kennedy Bridge, a dozen middle school students gathered around a burly man with a ponytail and a goatee. This was Ovidiu Grozav, coach of two flag rugby teams — one boys, one girls — from Intermediate School 392 in Brownsville, Brooklyn, and he was giving his boys a few words of encouragement before their first match.

They were one of 70 teams in and around New York City who were there on a blustery Saturday morning in early June to compete for the eighth annual Rugby Cup. Each team wore a jersey corresponding to a national team playing in the 2015 Rugby World Cup. The boys of I.S. 392, almost all of them black, represented Romania, their coach’s homeland.

“We can win this,” Coach Grozav implored. “We know what we have to do. Keep it simple. Play what you see.”

It’s a scene that would have been hard to imagine 10 years ago: nearly 900 city schoolchildren of varied ethnicities from every borough playing a sport that is associated mostly with territories of the British Empire and is named for the elite British school where it is thought to have begun.