Parents and school administrators lose sleep when trying to keep children safe from strangers, but often it’s the people they know that pose the biggest risk.

The issue of bullying is always with us, but it often takes a tragedy like the suicide of Phoebe Prince to bring it back to our attention. She was the South Hadley, Mass., 10th-grader who hung herself after what has been described as relentless harassment from her peers.

Prince’s death has led the Massachusetts Legislature to pass a law that toughens penalties for bullying and creates a legal obligation for people who come into contact with children to report bullying when they see it.

It shouldn’t take a tragedy for people to act, however. Less notorious, but equally troubling bullying, goes on in schools all around Maine. The pain felt by Prince is probably being endured by other kids who are forced to accept it as a consequence of going to school.

Schools are taking a lot of steps to combat bullying, but this is not something that can be addressed by passing a policy, or in the case of Massachusetts, a new law.

What is important is that bullying be taken seriously, and that everyone — not just teachers and coaches, but custodians, parents and other students — recognize that they have a responsibility to stop it when it occurs.

This is not only true for the traditional school bully, who physically intimidates a victim in person. It includes cases of cyber-bullying as well, in which computers, even the ones supplied by schools, are used to belittle and gang up on vulnerable kids.

That kind of bullying can be as destructive as the physical intimidation because there is no safety zone. The harassment continues after the child leaves school and follows him right into his home, in the form of instant messages and posts on social networking sites.

School administrators can’t be everywhere. But it is nearly impossible for prolonged and persistent harassment to occur without someone who is not involved finding out about it — someone who could speak up and stop it before another tragedy occurs.

We all share that responsibility when it comes to bullying, and we should take it seriously.