Local schools are being warned to prepare for a worst-case scenario after the deadliest armed school attack in United States history.
Rotorua schools have procedures in place in case an armed gunman threatened their students but hope to never need to use them in real-life situations.
John Paul College principal Patrick Walsh said schools needed to be realistic.
"I hope that [a mass shooting] would never happen but I think we have to be realistic and expect that it probably will and make sure that we do have best-placed measures to prevent that from happening,'' he said.
Twenty children and six teachers were gunned down on Friday morning (local time) at Sandy Hook Elementary School in Connecticut.
Shooter Adam Lanza, 20, entered the school armed with a rifle and two semi-automatic pistols. Among his victims
were eight boys and 12 girls _ all aged 6 and 7. He eventually turned a weapon on himself.
Mr Walsh, who is also head of the New Zealand Secondary Principals' Association, said all schools should have an emergency plan in place to deal with an armed intruder incident.
"Most schools now have developed a comprehensive lock-down procedure in their schools.''
When this happens, all classrooms are locked. Students and teachers hide under their desks or huddle in a corner. The school intercom system is turned on and no one is allowed to leave their classroom until police present themselves at the door.
He said some schools had supplied their building plan to police in case an armed intruder entered the school.
School building plans held by the Education Ministry could also be accessed by police in emergency situations, he said.
"I hope we don't get to the point that they have in the United States, where you have to hire security guards outside the school and big gates and you check people coming in and out and metal detectors.
"[But], that's the way the Western world is trending and I just think that's a sad indictment on society.''
A Rotorua primary school went into lock-down last year after reports a man armed with a sawn-off shotgun was in the area.
Selwyn School, which is located on Old Quarry Rd, was alerted to the incident by police.
The school was in lock-down for about 45 minutes before being contacted and told the "domestic incident had been sorted'', principal Tony Pope said.
Mr Walsh said his school had run a lock-down drill two years ago.
The armed offenders squad, police dogs and the ambulance service all participated, he said.
Students were able to practise how to behave in an armed incident, Mr Walsh said.
Westbrook Primary School principal Colin Watkins said schools regularly went through their lock-down procedures with staff and children.
He said Rotorua schools prepared themselves for a "major catastrophe'' of all kinds from natural disasters to an armed offender coming into the school.
He said it was important to prepare for the different incidents even though they hoped to never need to in a real-life situation.
Mr Watkins said schools practised their procedures at least twice a term and pupils knew the importance of following them.
He said that while he was working at a school in Northland, a man who was on methamphetamine had come into the school with a taiaha and the school was put into lock-down.
Mr Watkins said the man soon discovered he didn't have an audience and left.
Police have also said previously that an armed "shooter'' incident was a matter of when, not if, at a New Zealand school _ be it a deranged student or angry parent.
Attacks in schools
2009: 17-year-old student at Auckland's Avondale College stabbed a Japanese teacher in front of about 20 students.
2010: 13-year-old boy at Te Puke High School stabbed a maths teacher in the neck and shoulder.
2010: 15-year-old Hamilton Girls' High School student brought a knife to school and threatened to kill students.
2012: Upper Hutt school principal was assaulted by a 39-year-old male in his office.