Education Minister Anne Tolley is writing to schools demanding action on bullying after serious assaults on students.
Just this month two teenagers were taken to hospital after schoolyard attacks.
On March 8, a 15-year-old girl was punched and kicked as she walked home from Wanganui Girls' College.
She was hospitalised and said the attack had left her unconscious, bleeding from the ears and extensive bruising. The assault was filmed.
Also this month, a teenager was hospitalised after being beaten in another schoolyard fight.
The attack on the Lynfield College student was filmed on a cellphone and shared.
Prime Minister John Key said the internet and mobile phones had changed the nature of bullying but schools had to do everything possible to combat it.
"I think all New Zealand parents demand that their school is a safe environment and principals have a responsible to ensure that environment is safe," he said.
"The sorts of scenes we've seen... are worrying me a great deal. I worry about bullying, I worry about youngsters going to school and being intimidated by others, it's thuggish type behaviour that needs to stop."
Mrs Tolley would write to Boards of Trustees and remind them they were legally required to deliver a safe environment.
"I know what their legal responsibility is, by writing to them I am outlining very clearly the Government's expectation in this area," Mr Key said.
He also expected principles to work with staff, students and parents to ensure policies were sufficient and the Education Review Office would be asked to increase monitoring.
"We need to understand what happens when bullying gets out of control and that is when taken to extreme some youngsters take their own lives. I am not going to sit back and let that happen without at least trying to improve the environment."
When it came into office the Government dropped some anti-bullying programmes saying they were ineffective.
Mr Key said he wanted all relevant parties to get together to find solutions that worked and Mrs Tolley would head that.
"I don't think it's an issue actually of cash I think its an issue of attitude and whether we are prepared to stand up and act take a stance against bullying."