Editor's Note: To protect the kids' confidentiality, pseudonyms and photographs of models have been used.

Last spring, a teen posted an invitation on Facebook for a party in Northern Virginia. The host included the time and address and wrote: “I’m having a somewhat small group of peeps over and we’re chilling and having dance partys and sharing some cheese platters. BRING CHEESE PLATTERS because we cant use my cheese.”

“Cheese platters,” of course, is code. It’s an unwritten rule among teens that you don’t talk about parties on Facebook. That tips off the grownups.

“I haven’t been to a party in forever—every single one has been busted because of Facebook,” says Becky from Madeira. Kids post events for theme parties where there’s clearly going to be alcohol. “How easy is that for a dean to find?”

Cops are on Facebook, too. Montgomery County police officer William Morrison says the alcohol-enforcement unit creates profiles, friends high-schoolers, and searches Facebook for party talk.

“If we can, we try to shut the party down beforehand. If we can’t—we’ll show up,” Morrison says. “When we go to the house, they usually ask us how we found out. We say, ‘You told us.’ ”

Sometimes police get a tip on parties from an ex-boyfriend or ex-girlfriend or a kid left off the invitation list. “Revenge is sweet among teens,” Morrison says.

After weekends, Facebook profiles fill up with party photos—often teens posed proudly with beer cans. Camera-phone candids of party action also end up on profiles, including some that make kids nervous. “Every time you go somewhere, you’re thinking, what if your parents saw that?” says another Madison High sophomore.

A photo of a teen who’s drunk or making out might not make waves if it weren’t for a Facebook feature called “tagging.” A tag attaches a name to someone in the photo—and can broadcast the picture to other members via newsfeed.

Even teachers worry about Facebook photos. After a school banquet, a group of parents asked a Montgomery County teacher to pose for a picture with their daughters. The teacher stood with his hands behind his back while the students huddled around him.

“All I could think about was Facebook,” he says. “People do funny things on the Internet—and I end up in a scandalous pose with a high-school girl.”