Secondary school principals want the power to search students' cellphones and laptops, saying the battle against cyber-bullying overrides privacy concerns.

They also want more power to deal with bullies' activities outside school, where attacks have been caught on camera and posted online.

Secondary Principals' Association president Patrick Walsh told Fairfax the association is working with the Ministry of Education to give principals the power to confiscate phones, laptops and digital devices.

One in five children suffer from cyber-bullying and the effects could be devastating, he said.

The association wants schools be given the power to discipline students caught transgressing outside school, as some parents could not longer control their children and police were under-resourced.

"If we catch them outside the gate, whether it be videoing a fight at the park or smoking at the dairy, we want to be able to deal with that."

But Massey University researcher Anne Ryan said the punitive approach would not eliminate the problem.

"There is a real danger of a blame culture. Not just the bully, but the victim, is seen to be responsible."

More research was needed into how the school system might be reinforcing student power struggles, she said.

The Law Commission wants new laws to combat cyber-bullying, making it an offence to incite suicide, maliciously impersonate another person or publishing intimate photos without consent.

Justice Minister Judith Collins has said she is treating the issue as a priority.