The oldest team in the NBA gave the youngest a lesson. 

The tanking Nets — deep into a youth movement — got spanked by the venerable Clippers 121-105 on Friday at Barclays Center. 

With a record five first-round rookies — all but one of whom played — the Nets learned some valuable lessons against Los Angeles. They just weren’t easy ones. 

James Harden put on a show with a game-high 31 points on 10-for-13 shooting, getting to the rim at will. The future Hall of Famer had 15 points in the first quarter alone, when he helped put the Nets in a 16-point hole. 

Kawhi Leonard, who was questionable with a sprained right ankle, added 13 of his 26 points in the fourth quarter. And even with 40-year-old Chris Paul sent home, the Clippers put on a clinic in cutting up what had been a stout Brooklyn defense. 

“The reality is you can explain the game plan, but until you don’t go through it, that’s how you learn,” said Jordi Fernández. “Those minutes were very valuable because you see those guys and sometimes you guard and you’re like ‘Oh, that was good defense.’ But for us, because we’ve seen them do it, it’s like that’s not good defense because they’re going to keep scoring, because they’ve done it all their careers and they’re going to keep doing it. So it’s good. That’s how you learn.” 

The Nets were found wanting. 

They coughed up 59.2 percent shooting and 58.3 from deep, diced up by the Clippers. 

The rebuilding Nets average a league-low 23.7 years old, per NBAage.com, while the Clippers are the only team in the league at 30. 

Lottery pick Egor Dëmin led the Nets with 19 points and three steals on 5-for-10 from deep. Michael Porter Jr. added 18 points, six assists, five rebounds and four steals, but had a rare off night, shooting 0-for-9 from behind the arc. 

“It’s very rare. It’s going to happen once every five years that Mike just misses nine 3s,” Fernández said. 

The Nets (11-24) are fifth in the lottery standings, but are closer to ninth than they are to fourth. Brooklyn stayed two games behind the fourth-seeded Wizards, who lost to the Pelicans. The Nets are half-game ahead of the Hornets, and one ahead of the Jazz. 

The Clippers are 8-2 since a 6-21 start. 

Harden, who broke up the Nets’ Big 3 when he was the first to ask out, led the way. 

“Some great memories. We had an opportunity to do something special,” Harden said of his stint in Brooklyn. “Me personally, I was just injured. And that was the first time in my entire career that I wasn’t able to stay on the court and be effective like I can be, like I am. So for that part, it was a little frustrating. But some great experiences those two years or whatnot, obviously it was COVID, so the world was in a crisis. But, this organization has helped me and I appreciate them.” 

The Nets coughed up a 16-2 run to fall behind by 16 midway through the first quarter. Then they conceded 14 unanswered points in a Clippers blitz that spanned from the end of the first well into the second. 

Even Brooklyn’s all-time leading scorer came back to haunt them. Rookie Danny Wolf drove the baseline late in the third, but got his shot blocked by 37-year-old former Nets center Brook Lopez. 

“They just made it tough for us. They were loading up, doubling Mike, doubling [Cam Thomas]. They had a real good game plan, they were locked in on our sets and we weren’t able to generate a whole bunch of clean looks and get into a really good flow offensively,” Nic Claxton said. 

“They just came out and were hitting shots. You need to start off better, especially playing against such a talented team like the Clippers.”