Glen Cove High School basketball player Khalil Zachary drove past his defender, pump faked, then shot the ball.

It was just a friendly game at North Shore High School in Glen Head, but it was held for a serious matter: supporting teens who have aged out of foster care.

North Shore junior Ryan O’Day, 17, organized the “Teens Gotta Believe” event, which included a three-on-three basketball tournament, to raise money through registration fees and donations for You Gotta Believe, a Brooklyn-based group that aims to find permanent families for foster children.

About 100 people, including 60 youths, attended the event, which had also included a track and field component that was canceled due to Saturday’s rainy weather.

A DJ played pop songs as the kids took jump shots and loosened up for the games.

O’Day said many foster teens are left without a strong support system once they turn 18 and age out of the foster-care system.

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“I want to start a conversation,” he said.

He said he was inspired after reading “Etched in Sand,” a memoir written by Regina Calcaterra, who grew up on Long Island in the foster-care system.

“It was a life-changing book to read about abuse and homelessness,” O’Day said. “People raise money for cancer and other illnesses, but not necessarily for foster care.”

O’Day’s mother, Jillian O’Day, helped to organize the basketball tournament.

“I’m supporting my son,” she said, noting more than 20 teams signed up to play.

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The author of “Etched in Sand,” Calcaterra, lauded the teen’s efforts in a speech at the event.

“I never thought a young man would read my book and have it resonate with him,” said Calcaterra, who once served as Suffolk’s deputy county executive and as executive director of Gov. Andrew M. Cuomo’s Moreland Commission.

She added: “For him to be able to put on the event” is great.