When Elle, 39, and her husband dropped off their 9-year-old son and 8-year-old daughter at camp three weeks ago, the Long Island parents were only too happy to wave goodbye to their kids for several weeks. Later that day they boarded a party bus with 30 friends and plenty of booze to go see Dead & Company at Citi Field.

“As soon as [our children] left, we’ve been in nonstop [party] mode — it’s seven weeks of freedom,” says Elle, a fitness instructor whose two kids are away for the first summer ever, leaving her to enjoy parties with pot, magic mushrooms, ecstasy and group sex.

“This is the first time in nine years I’m not having to be a mom — I want no responsibility,” says Elle, who, like many in this story, declined to give her last name for privacy reasons. “Some friends have swingers parties — I’ve seen group sex . . . It’s no pressure, go with the flow. It’s summer.”

Traditionally, it’s the kids who run amok when Mom and Dad are out of town. But these days, it’s the parents who are home alone and going skinny-dipping while their youngsters are away at camp.

“When you know your children are happy and safe, you can let loose,” says Melanie, 38, a Long Island mom who shipped off her 12-year-old and 10-year-old a few weeks ago. It’s her second kid-free summer, and she and her husband wasted no time popping bottles.

“We took the boat to a bar and literally spent all Sunday afternoon drinking,” says the VP of a fashion company. Other exploits have included a night out on Fire Island with girlfriends, where they closed down the bar at 5 a.m. And the best is yet to come, she says, noting one set of parents who host an epic bash every year.

“The couple goes all out — with naked girls and midgets,” she says.

‘Friends have swingers parties… [its] go with the flow, it’s summer.’ - Elle, a Long Island mother

For parents who had children at a relatively young age, having the kids away at camp helps them make up for lost time.

“It’s your second chance if you didn’t get to do things when you were younger,” says Lori Zaslow, 39, a relationship expert and co-founder of matchmaking service Project Soulmate.

“There’s a price you pay to have a life being a parent,” adds the Upper East Side mom of two, who has been married 16 years. “I can do whatever the f – – k I want, and I will. I’m not going to waste a minute.” The relationship guru makes a suggestion: “This is the time to have sex in the kids’ bedroom and have fun!”

She’s typically quite modest when her kids are around, but all that changes when they leave.

“I can dress more promiscuous — I’m literally going to put on my tightest dresses,” she says. “I’ve never worn a bikini in front of them — I don’t want to be too exposed. Now I’ll be walking around naked.”

But, says Zaslow — who works as a relationship expert — for some of her peers, having the kids away doesn’t make for summer fun.

“Many couples realize they have nothing in common anymore,” she says.

That’s not the case for Tara, 44, a mom of two pre-teen girls, and her husband. The couple uses their child-free time to really reconnect with each other.

“First rule is, clothes come off when you get in the house,” says the fashion executive, who also lives on the Upper East Side. “The kids are out of the house — and you want to have sex every day. It’s the fun of being able to do it — it’s a game.”

She and her husband also enjoy regular “Playboy party” dinners with their friends: The women don as little as possible and the men dress like Hugh Hefner. Or there’s “tennis and tequila” at the club.

“It feels like we’re kids at an adult camp — we’ve earned it,” she says. “We’re great parents, but sometimes kids need a break from their parents, and parents need a break from kids.”

Gary Katz, a Chelsea-based therapist, says it’s healthy for parents to have a good time.

“Everyone has a little badass in them,” he says.

But sometimes the good times can turn bad.

“I know a professional Wall Street guy who got arrested for urinating in an alleyway outside a club. He spent the whole weekend in jail,” says Katz. “It was the week after the kids went away to camp.”