The idea is simple enough: Children do everything they might at a sleepover, down to changing into PJs. But instead of staying the night, they return home to sleep snug in their own beds, and wake up the following day, presumably rested and un-cranky.
"It's much easier on the parents," allows Megan Gorman, whose daughter, Evie, 11, has favored half sleepovers, as the family calls them, in recent years. "It allows them to get a little more sleep." And that, Gorman adds, makes life so much more pleasant the next day, when schedules are often jammed with activities.
Janice Hayes-Cha, whose daughter Joanie was invited, still cringes at her family's one and only sleepover party a couple of years ago. It was for her son, who had invited half a dozen 11-year-old boys to spend the night.
"They all came running up the lawn with Nerf guns," she says. "It was as if we were being invaded." Once the boys came inside for the night, she remembers a lot of jumping that she and her husband could hear overhead from their bedroom - into the wee hours. "They were up all night. We were up all night."
Hayes-Cha recalls her husband saying, "Never again."
As she puts it, only half joking, "Nothing good happens after 11 p.m."
Ever since, sleepunders have won the day - or rather the late evenings.
In a survey posted this year on the opinion website tellwut.com, about 43 percent of 1,630 respondents agreed that a sleepunder was "great for younger children who are unable to spend the night away from home quite yet."
At the same time, more than a quarter thought sleepunders go too far and strip the fun out of sleepovers. Remember those slumber-party gab sessions, ghost-story marathons, truth-or-dare contests?
To hear psychologist Robert Epstein tell it, sleepunders gnaw at the very fabric of American family life.
"It shows a lack of trust in children, that they're not mature enough or competent enough to stay safe overnight at a friend's house," says the senior research psychologist at the nonprofit American Institute for Behavioral Research and Technology in Vista, Calif., and former editor in chief at Psychology Today.
He allows that a sleepunder by itself is "no big deal. But look at it from the perspective of an ongoing trend of being overprotective, and it is a big deal. It becomes one of hundreds of practices."
In his 2010 book Teen 2.0: Saving Our Children and Families From the Torment of Adolescence, Epstein documents the rise of what he calls the infantilizing of young people. Since the Civil War, adolescence has emerged as a stage in life governed by an increasing number of restrictions, he says. From laws that seek to control the behavior of young people (tattoos and tanning-salon regulations, for one) to, yes, sleepunders, he argues, we have raised a generation that's hopelessly helpless.
Back at the Gormans', however, the tween girls don't seem to be lacking for independence or cut-loose free play. Several say they enjoy traditional sleepovers with just one or two friends - where actual sleeping is a real possibility - but when bigger groups are involved, sleepunders make more sense, they say.
"You don't leave anyone out," Atara Saunders, 11, says.
For Evie, the point is to have a blast with her close girlfriends. Sleeping over, or not, doesn't matter to that equation very much, she says.
Besides, "I'm not really comfortable sleeping in other people's houses," she says. "I like sleeping in my own bed."
In fact, her mother says, that was the genesis of the half sleepover for her family. Evie had spent the night at friends' homes in this tight-knit pal group since preschool. "But as she got older, she started to get more particular about where she sleeps," Gorman says. The half sleepover seemed the perfect solution.
Gorman doesn't dispute that members of her generation are prone to being control freaks. Online, parents have said they prefer sleepunders because they worry about a lack of supervision (think R-rated movies in the wee hours and overdosing on junk food) or feel uncomfortable leaving their child with adults they may not know well.
But for Gorman, the half sleepover just makes it "easier in the morning."
Perhaps, she says, it's a sign of our sleep-deprived, jam-packed days, and weekends, more than anything else.
Even these tweens seem to get the importance of 40 winks.
"If I stay up all night, I get cranky and annoyed," Emily Warden, 12, says.
"A half sleepover is like hanging out but you stay later," adds Emma Fishbein, 11, who notes that she has an early gymnastics session the next day, so best to get some shut-eye.
For Terry Cralle, a registered nurse and a clinical sleep educator based in Richmond, Va., anything that detracts from catching one's zzz's demands careful review.
"I would be very opposed to sleepovers, knowing what we know now," she says. She applauds the sleepunder. "It's very astute of parents to retire that childhood ritual."
The National Sleep Foundation recommends 10 to 11 hours of sleep for 5- to 10-year-olds and 8½ to 91/4 hours of sleep for tweens and teenagers.
One of the most important factors, say sleep experts, is consistency seven days a week. "The idea of a sleepunder . . . is more in keeping with the belief that a stable or consistent bedtime is healthy," says Joan E. Foley, a sleep researcher at Temple University.
For children - and parents.
As the parents nudge the girls out the Gormans' front door, one mother says: "Come on, let's go. It's getting past my bedtime."