Most of the parents believed their girls are still virgins, but Natalie's parents learned just how close to the brink their daughter got with a boy who didn't even like her.
"That the only reason he even talked to me was because there was a chance that he might get something out of me, and that I was totally not attractive, or his type, or anything," Natalie said on tape. "And um, and that was kind of a wake-up call."
Natalie's mom, Jana, cried as she watched her daughter talk about her heartbreaking experience. "Shocking," Jana said.
Natalie's dad, Jim, said he thought his daughter could handle herself with boys and wouldn't put up with being treated poorly. But after seeing the tape, he said, "I think we're a little smarter now on the real Natalie."
Rubenstein told Jim and Jana that they know the real Natalie, but "it's just that the world that she lives in ... is different. ... So don't think it's her."
Another parent, Elaine, watched her daughter, Tracey, talk about losing her virginity to her best friend -- and getting her heart broken.
"It's painful for me because I ... know she really cared about him, and it just, it hurts me, because his parents almost came up to me in my face and said to me, 'You are a bad parent, because you're not like a parent to your daughter, you're more like her friend,'" Elaine said.
But Elaine wondered why only her daughter was looked upon as the "bad" person.
"And it's not my child that's corrupting yours, it's yours that's as equal in this as mine is. ... It made me mad," she said.
But Tracey's stepdad may not understand and might punish her when he hears her confession, Elaine said.
"I think he expected for her to stay pure until she was married," she said. "But you know what, this is not realistic. That's not living in the real world, just like his [the boy's] parents don't live in the real world."
And then there was Tiffany, who had been so bold the night before, talking about engaging in behavior to please boys.
When her mother, Christine, watched the video, she said she was bothered that the girls were so easily manipulated by the boys. "I question why would they feel that they need to be manipulated to impress a boy or excite a boy?" she said.
In many cases, the girls felt it was easier to tell their secrets on national TV among strangers than it was to tell the people who love them most in the world. But they also longed to feel safe in confiding in their parents.
"It's just so embarrassing for them," Rubenstein said. "That's the thing, to us as adults might feel like, you know what, we've all been through it. It's not a big deal. To them, it's a lot of times, the first time they're going through things, and it's a big deal."
It seemed that when both the parents and teens took those first steps to talk about the details of sex -- without anger or embarrassment -- they found it easier to move ahead and talk about how to deal with difficult situations and stay safe.
As Natalie's dad, Jim, said after the experience, "This was huge. ...I hope we can do this again."
And Natalie, too, was relieved about having the conversation. "It has definitely shown us something was missing in our relationship and we definitely needed to patch that hole up before it was too late," she said.
Since the sleepover, "Primetime" received updates from many of the girls, who said that revealing so much on camera was a life-altering experience for them, and that it actually improved their relationships with their parents.