Leslie Levine of Northbrook, Illinois, never thought she'd drag her daughter home from a sleepover. But she did when her 12-year-old called, nervous because her friends were going out to toilet-paper some local houses. "It made me wonder about the girl she was staying with. Do I really want my kid around friends who think that's okay?"

It's inevitable that at some point your child will befriend someone who doesn't share your values. "Kids this age are becoming more independent and may be attracted to a 'bad' best friend as they start to break away," says Barbara Polland, a professor of child and adolescent development at California State University at Northridge. Making a rebellious pal doesn't mean your child's headed for trouble. To figure out if he is:

Consider what's fueling a surprising friendship. Maybe your kid likes the thrill of hanging out with someone more adventurous, or the fact that his new friend is a star athlete, not the fact that he seems "dangerous."

Invite the new friend over. Chat with him and see how he acts in a supervised setting. He may not be as bad as you think.

Don't criticize the friend in front of your kid. And don't forbid your child to see him. The more you disapprove of a pal, the more attractive he'll seem -- and the less your child will confide in you about their escapades.

Spell out your expectations. Be clear about what rules you have for your child -- like when he's supposed to be home and how you expect him to treat others -- and what the consequences will be if he crosses the line.

An exception to the "don't forbid" advice: If you see evidence over time that your child's new friendship is indeed dangerous -- say, your kid's starting to steal or smoke as a result -- break it up. Your child may seem outraged-but on some level, he'll probably be relieved. And he'll definitely be better off.