We usually don't see girls behaving viciously and brutally. But when high school seniors tortured junior girls at Glenbrook North High School in Northbrook, Illinois, the world took note. Why would girls do this—and what can parents do to help their teenagers?

Family psychologist Dr. Michael Riera explains why parents should talk with their kids, and Rosalind Wiseman shares her insight after having spent more than a decade talking to teenage girls.

What's the Motivation?
Cliques, gossip, feelings of revenge and exclusivity all contribute to the social culture of teenage girls. With hazing, girls use fear to seek respect, says Wiseman. "Older girls say to the younger ones, 'If you want to take our place when we're gone, you have to humiliate yourself to come to this place of power." Some of the younger girls even feel honored to be targeted.

Talk with Your Teenager
While adults have experience with group mentality, most teenagers don't. "Explain that when we're with a group, we will do things we normally wouldn't do on our own," says Dr. Riera. Talking with your child can help him or her realize that it's difficult to dissent—but they'll realize that they do have the choice to do so. Ask your teenager, "If you were in this situation, what would you do?"

Establish Consequences
Children need to learn from their mistakes. "All kids have to have consequences," says Dr. Riera. "When we don't let them have consequences—when we get the legal system working for them so they don't have to face consequences—we're saying, 'You can't handle it,' rather than 'You face the consequences, you can handle it, you can become a better person.'"