Frances Tiafoe stood with his hands on his hips and feigned disappointment on Thursday after his partner, during a doubles drill, dumped an overhead into the net.

Moments earlier, on the same courts at the Junior Tennis Champions Center (JTCC) where he learned the game not far from the nation’s capital, Tiafoe jokingly chastised another of his temporary teammates — all aged 10 or under — for not celebrating a good shot properly, explaining the importance of yelling and punching the air.

A semi-finalist at the US Open last year and now ranked in the ATP Top 10, he took part in the clinic with dozens of kids after a ceremony to announce the launch of The Frances Tiafoe Fund in conjunction with the USTA Foundation, the charitable arm of the sport’s national federation.

“I’ve wanted to do this for a long time,” the 25-year-old Tiafoe said. “I’m a product of this place. I’m a guy who was given a chance — who wouldn’t have really had one — and look what I was able to do with it.”

His parents emigrated from Sierra Leone in the 1990s to Maryland, where his dad helped construct the JTCC in College Park, then worked as a maintenance man there. So that’s where, and why, Frances and his twin brother, Franklin — who took part in Thursday’s on-court drills, too — picked up tennis. “This place was built in ’99. I’ve been here ever since. I’ve been here my whole life. I’ve played on these courts numerous times. I’ve spent so much time with some of these coaches, these mentors, people who have been here 20-plus years,” said Tiafoe, who is entered in the joint ATP-WTA hard-court tournament in Washington next week.

“All these little kids who come and see me — I wanted to be in a position to actually have an impact and not just sign autographs.”

His fund is starting with grants totalling $250,000 from the USTA Foundation and one of Tiafoe’s sponsors.