"I hate to think of what's out there. . . . There's so much out there that it's hard to know what's there," said Ken Blackstone, a Prince William schools spokesman. "But as public employees, we all understand the importance of living a public life above reproach."

It's almost like Googling someone: Log on to Facebook. Join the Washington, D.C., network. Search the Web site for your favorite school system. And then watch the public profiles of 20-something teachers unfurl like gift wrap on the screen, revealing a sense of humor that can be overtly sarcastic or unintentionally unprofessional -- or both.

Local school officials said they don't necessarily scrutinize Facebook when they conduct background checks on teachers. But in some parts of the country, they do.