Sleepy guests and frazzled parents are what most sleepovers generate. Kids are thrilled to spend the night with a group of friends, snacking, chatting and playing. Who wants to snooze through all that fun?

But with children as young as 4 or 5 now hosting group sleepovers, some worry the downward trend will encourage more risky behavior in adolescents with a "been there, done that" attitude. Sleepovers — what parents knew as "slumber parties" — are de rigueur for the tween and teen set.

"Sleepovers are to 12-year-olds what driving is to 16-year-olds," said Laura Kastner, a University of Washington clinical professor of psychiatry. "That personal autonomy jump is pretty exciting."

Sleepovers tend to peak in middle school, when young teens are socially active and want independence from parents but don't have their own transportation. Especially popular with girls, some report sleeping over at friends' houses at least every other weekend, often staying up all night.

It's also the age when some kids push boundaries. In the new PG-rated "Sleepover" movie, a group of 14-year-old girls make a date with a man they met over the Internet, sneak out of the house, steal a car and dress up so they appear old enough for a club.

This spring in California, a 14-year-old girl died after experimenting with the drug ecstasy during a sleepover and in another incident, two 13-year-old girls left a sleepover at 1:45 a.m. to meet 19- and 20-year-old men, who were later charged with committing lewd acts with a child.

Most sleepovers aren't likely to turn so wild or dangerous, but parents should realize "every child you add drops the group IQ level," warns Kastner, who specializes in teen issues. "Risk-taking comes up when kids are together in a group."

"I wouldn't be surprised if half the mischief teens get into — at least girls — have a sleepover setting," said Doris Fuller, an Idaho mom of two and co-author of the new book, "Promise You Won't Freak Out: A Teenager Tells Her Mother the Truth About Boys, Booze, Body Piercing, and Other Touchy Topics." (See story on C10.)

"I sleep, which is something teens don't do a lot of," Fuller said. "That's eight hours of unsupervised time. Sex, drugs and rock 'n' roll only happen when there's no parent to oversee them."

Indeed, "the theme for parents is vigilance," Kastner agrees. "Whenever parents are surprised by what goes on at sleepovers in seventh or eighth grade, what I always hear is, 'I didn't think it would happen so soon,' " she said. "Don't be naive: When you sleep, keep a third ear and be ready to get up and check the windows and doors."

Fuller relates how her then sixth-grade daughter and friends defied her lights-out policy during a sleepover and visited an Internet romance chatroom at 3 a.m. posed as a Playboy bunny. At another sleepover, a group of girls ran around the neighborhood naked at 1 a.m. with Fuller completely unaware.

"Someone said, 'I dare you to streak,' " Fuller's daughter Natalie wrote in "Promise You Won't Freak Out." "Someone else said, "I'll do it if you do it with me.' The next thing we knew, all five of us were bouncing down the street butt-naked.

"In any group, the craziest or sometimes the stupidest person sets the tone for everyone else," Natalie explained. "Most of us need that Single Brave Person to get the ball rolling."

Kastner advises parents to look every tween or teen in the eye and say, "I'm counting on all of you to respect my house rules." Get an acknowledgement from each one.

"It's not a guarantee, but it's a lot harder to violate," Kastner said. "There's likely to be two or three in the group who won't go along with a plan because they figure 'she knows what we're up to.' It's a preemptive strike."

Natalie, now 18, says it's hard for parents to know which sleepovers are innocuous and which are risky. She's been to both girl-only and co-ed sleepovers that were alcohol-free and others where kids drank. "Parents don't usually know what's going on," she said. "At one 16th-birthday-party sleepover, we drank a ton and the parents never knew even though they were upstairs the whole time."

Other times the girls — usually a group of five friends — played games, watched movies, cooked, painted each others' nails and talked, Natalie said.

Games, DVDs and junk food are sleepover mainstays for both boys and girls, with a new high-tech twist. "Thirteen-year-olds do the 'IM and call girls' thing until late at night," noted Trish Kinney, a Clyde Hill mom of boys ages 7, 10 and 13. "They make phone calls until about 11 p.m., then it's all IM until the wee hours. The girls are usually at one house and the boys are at another, in constant communication."

While they're instant messaging, the boys also play video and computer games and watch ESPN or MTV, Kinney said. Another favorite is listening to CDs and burning mixes for each other.

Cellphones make it easy

Sometimes younger teens sneak out to meet the opposite sex but for older teens, the more common deception is a sleepover as cover for partying or spending the night at a boyfriend's house, Natalie said. "You just call your friend and say, 'I'm sleeping over at your house tonight; you know the drill.' "

Don't parents figure it out? "Cellphones make it really easy for us," she explained. "We just say, 'I'll have my cellphone if you need to check in with me.' "

Savvy parents call the other parents directly: "There's no way we can cover up for that," Natalie concedes. Sometimes her mom even drove to Natalie's friend's house if adults didn't answer.

Another controversial issue for some parents is the co-ed sleepover. Wilhelminia Ripple's 2002 activity book, "Slumber Parties: What Do I Do?" lists the "seven stages of sleepovers," with co-ed sleepovers as the sixth stage and unsupervised co-ed sleepovers as the seventh.

Kimberly Whalen of Edmonds, a mom of four, let her 18-year-old son stay at an overnight party after prom but says "no way" to co-ed sleepovers for her 16-year-old daughter, Alexandra. Alexandra has sleepovers with friends a couple times a month and even hosts themed events, such as an Academy Awards sleepover where guests came dressed as "Lord of the Rings" characters.

Kastner advises parents not to feel shy about contacting host parents and setting up acceptable parameters. As a parent of two teens, she's assured parents of invitees that no, her older son and his friends won't be around for her daughter's sleepovers. Parents can also clarify supervision expectations, what movies or video games are slated and who will drive if outings are planned.

"Parents fold when kids berate them for checking up," Kastner said. "But you have a God-given right to do this between now and age 18."