There’s a picture of Joakim Noah that was taken by USA Today shortly after he won a state championship with the Lawrenceville School in New Jersey. He’s 19 years old but looks younger. His head is cocked and he doesn’t have scruff yet, and his hair is a springy mop of puffed-up curls, not long and flowing or tied up in a bun, as he would wear it in later years.

He’s wearing a Knicks jersey.

That’s really no surprise to anyone who knows Noah, 31, the former Chicago Bulls center who this past week agreed to a four-year, $72-million deal with the Knicks.

The son of French tennis champion Yannick Noah and former Miss Sweden Cécilia Rodhe grew up in Hell’s Kitchen, just a few blocks from Madison Square Garden, as a Knicks superfan.

“He’s going to be the biggest Knicks fan playing on the team,” said Bill McNally, Noah’s basketball coach at Brooklyn’s Poly Prep.

Yannick Noah, the 1983 French Open champion, was friends with Patrick Ewing and Joakim was in Knicks heaven; he loved the game and he loved talking Knicks with his coach. Long after he moved on to the University of Florida and then to the Bulls, that “what-if’’ scenario still played in his head.

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“This is something that we had spoken a little about even over the years,” McNally said. “Like, ‘do you think that would happen?’ ”

Though Noah’s name has been synonymous with Chicago basketball for the better part of a decade — he was the Bulls’ first-round pick in 2007 — the city of his birth courses through his veins. He visits often, maintains many of the friendships he made in childhood and still keeps in constant contact with McNally.

He spent only two years at Poly Prep — he enrolled there as a sophomore and his senior year was at Lawrenceville — but two months ago, when Noah was in New York, he had dinner at his old principal’s apartment. They talked about the Knicks. About that “what if.’’

“It’s one of the best things I’ve heard in my old life,” said Bud Cox, 62, who became head of the Upper School at Poly Prep the same year Noah enrolled. “The fact that he didn’t play professional basketball in New York was a sad thing for us . . . He was a huge Knicks fan.”

Cox did Noah’s enrollment interview in 2001, and the first thing he remembers was a wiry, impossibly tall young man. In his time at Poly Prep, though, something else became evident: Noah’s work ethic was even bigger than he was.

“I’ve never seen anyone work harder than Joakim,” said Cox, who taught for 41 years and moved to New Mexico shortly after that dinner with Noah. “And everybody loved him because he was a good person and he had a strong social conscience.” Noah was an “imp,” he said — fun-loving and a practical joker. Much of that still lives on.

McNally and Cox talk a lot about Noah’s character. McNally went down to see him in Florida once, he said, and watched Noah sign autographs for two hours. Another time, in Chicago, he saw Noah pop three kids and a coordinator for his charity, the Noah’s Arc Foundation, into the back of his Porsche. He had invited them to watch him play, and now he was driving them home.

Noah does “serious work” with his foundation, which reaches out to kids and encourages them to improve their communities, McNally said.

“I think that’s another reason he wanted to come back,’’ he said. “He thinks he can do good not just for the team but the city.”

But like any fan or coach — Cox coached, too — they also envision what Noah can bring to the team. McNally has no doubt that he’ll mesh with Carmelo Anthony and former Bulls teammate Derrick Rose; he calls Noah a “chemistry guy” who elevates others. They even played a little bit of the triangle at Poly.

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Cox brings up Anthony with enthusiasm, too, but seems especially excited about what Noah and president Phil Jackson can accomplish together.

“His being with Phil makes all the sense in the world,” Cox said. “They’re both cerebral, yes, but more than that, they want to make a difference in the world. They want to make it better.”

McNally says he plans to go to every Knicks game at the Garden. He was laughing, but he might be serious. Cox will fly in from New Mexico to watch him, he said, and he’ll be there when the Knicks play in Denver and Phoenix.

“There’ll never be a Knick that played harder than him,” McNally predicted. “This is going to be a tremendous thing for him . . . He’ll be so excited to put on that uniform.”

Joakim Noah. In a Knicks jersey. Again.