“All bystanders are not created equal,’’ Mullin says. “They run the gamut from a sidekick egging the bully on to a good Samaritan who steps in.’’ Most fall somewhere in the middle: They feel bad but don’t know what to do, she says. They need strategies as well as support from peers and adults.

With the growing understanding that bystanders - both children and adults - are key, more schools are engaging in training programs that emphasize the role they play. Mullin is also a program director for the Olweus Intervention Model, which has been adopted by more than 3,000 American schools, including about 20 in Massachusetts. Under that model, created by Norwegian psychologist Dan Olweus, the entire school - teachers, students, secretaries, custodians, cafeteria and playground workers - is trained to recognize and curb bullying.

“Bringing the bystander in was always the critical piece, and in America that response has been the most lacking,’’ says Nancy Mullin, executive director of Bullying Prevention Inc., a Natick consulting firm that helps schools combat the problem. “The stress has been on incorrectly pathologizing the bully: that they are social misfits and have low self-esteem, which we know is wrong.’’ Many bullies, she says, are the popular kids who have followers.

In the wake of the various school shootings of the past decade, the focus of curbing antisocial behavior has been on bullies and their victims. But a third group has emerged as even more critical: the bystanders. Now, schools, pediatricians, and others who deal with children are seeking to shift some of the responsibility for stopping an act of bullying to those who witness it.

“I think it’s very hard to be a bystander, because when you’re watching a bully, you’re not sure how or when to intervene. I think people are scared to intervene,’’ says Brigitte, who lives in Dover. “All it takes is one voice and maybe someone else will join in to stop it. I think there’s power in numbers. Bullies don’t like to be put on the spot.’’

But Brigitte - like every other kid - more often has been a witness to bullying than a victim. And she believes there’s no such thing as an innocent bystander: If you’re a spectator, you’re a participant. Still, she knows that helping out is easier said than done.

Brigitte Berman is 15 years old, nearly 5-feet-11, and a self-described science geek. “I’m in a robotics club, and I really like science, and I’m kind of tall,’’ she says. Because of all of that, she has occasionally been the victim of bullying. So she recently self-published a novel, “Dorie Witt’s Guide to Surviving Bullies.’’ Told in journal form, each chapter contains tips for victims.

Under the Olweus approach, adult witnesses also take more responsibility. “Bullying happens in front of or within earshot of adults most of the time, so they need to be the first responders and they need to be effective,’’ says Mullin. The sole responsibility, she says, shouldn’t be “dumped on kids.’’

National studies indicate that one-third of children have either been a bully or a victim, and nearly all have been bystanders. Marlene Snyder, director of development for the Olweus program in the United States, agrees that the majority can no longer remain silent, given the serious consequences.

“Bystanders are key. They need to know it is OK not to join in and that they can reach out to those kids who are being bullied,’’ Snyder says. “They can circle back and say, ‘Come sit with us. We’re sorry that happened. It isn’t right.’ It takes a lot of courage.’’

In a new policy statement from the American Academy of Pediatrics, Boston pediatrician Robert Sege defines the role doctors should play in bullying prevention. It is the first time the academy has included a section on bullying, including a recommendation that schools adopt the Olweus prevention model. Protecting children from injury, including bullying, is a key task of pediatricians, says Sege, who is chief of ambulatory pediatrics at Boston Medical Center.

“The brilliance of it is that Olweus identified that the key to stopping bullying was activating the bystanders,’’ says Sege, who is also medical director of the hospital’s child protection team. “The kids make a social contract that they’re going to protect the more vulnerable ones against bullying.’’ By doing so, he notes, the bystanders’ view of the bully changes from “top of the heap to the bottom. They see that the bully has a problem managing his or her behavior. They have reinterpreted the bully’s behavior as weird.’’

Sege says pediatricians must be ready to ask key questions of patients at routine checkups, as he does: “What’s going on at school? Do you feel safe there? What happens on the playground? Do kids get picked on?’’ They should also counsel parents about bullying, and be ready to call the school principal on a patient’s behalf, he adds.

This month, a Springfield mother testified before a congressional subcommittee in the wake of her son’s suicide following relentless bullying at school. Sirdeaner Walker told the panel she supports a bill that would require states that receive grants for safe and drug-free schools to invest in bullying prevention programs.

Last year, Brigitte’s sister, Margot, was the victim of cyberbullying by girls at her school. “Gay’’ or “lesbian’’ is the slur du jour: Margot, 13, and her group of friends were targeted by those who posted on Facebook or AIM. “They said rude things and made lesbian comments,’’ says Margot.

Jane Berman, the girls’ mother, took action. She knew the offenders’ parents and felt comfortable talking to them about it. The girls apologized; one even sent a handwritten letter. Berman thinks talking to the parents or school officials is a good solution. “I was taught in my generation just to ignore it,’’ she says. “But that really never worked.’’

Margot, who will enter the eighth grade in the fall, sees lots of name-calling on the school bus. “If we see it going on, we always say, ‘Stop that. It’s not nice,’ or we say something to the person being bullied, like, ‘How was your day?’ ’’ Still, she says, most kids stand by and watch. “They’re afraid to speak up.’’

Hasan Jafri, 17, will soon enter his senior year at the Dexter School in Brookline. His school takes a zero-tolerance approach to hazing and sexual harassment, and he says there’s not much bullying. But when he was younger, he witnessed some taunting. “I think the bystanders are important, because in my opinion they really can stop it or they can contribute to it,’’ says Jafri.

As for Brigitte, she has witnessed the “mean girl’’ syndrome, where so-called friends turn on one another, excluding first one, then another girl, while spreading gossip. “I think it’s happened to almost every girl,’’ she says. “You don’t even know what brings it about.’’

She believes that out of the group of gossipers, one or two will be uncomfortable about it. And they’re obliged to do say something - either to the shunners or the shunned. “Just walk away and talk to that other girl,’’ she says. “It’s difficult because you don’t want to be shunned, either. But I feel you’re obligated. You can’t just watch as people just trash another person.’’

© Copyright 2009 Globe Newspaper Company.