The Ministry of Education is warning schools not to practice violent offender drills with their students because they might cause fear and anxiety.
It also told them that teachers cannot stop parents taking their children from classrooms during emergency lockdowns, but confirmed they can allow children to leave locked rooms to go to the toilet.
The advice comes in guidance and legal information the ministry has been developing since the Christchurch mosque massacre in 2019 prompted a lockdown of the city's schools and early childhood centres.
In recent years, lockdown drills have become increasingly common at many schools, and some have had to put their preparations into practice when suspected offenders have passed near or through school grounds.
The ministry's guidance stated schools should prepare for emergencies, including situations where violent offenders were in the area.
"Drills on what to do in violent situations should be practised, but at a time that children/young people are not on site as the drills may cause undue fear and anxiety," the guidance stated.
"An attacker on your premises may require a combination of responses. Delaying their access to potential victims should be a priority.
"Depending on the size of your site/campus, and the ages and capability of your children and young people, can some groups move away from potential harm (escape)? What messaging can be used to signal some groups could escape? Consider a verbal warning system directing people away from the area where the danger is. For example at a secondary school "aggressive intruder in C block… move away from this area".
The guidelines noted that schools and early learning centres should tell parents what their emergency arrangements were, including arrangements for collecting children.
That was a problem for some Christchurch schools, when parents tried to collect their children during the lockdown in 2019.
Separately published legal information said schools and early learning services had a responsibility to keep staff, children and young people safe.
"This responsibility needs to be balanced against a parent's right to take their child out of the school or early learning service should they wish to do so. Opening the school or early learning service to a parent could be a risk when there is unknown danger," it said.
"If despite being advised of the risks in letting children out of school or an early learning service in the midst of a lockdown or shelter in place event, the parent or caregiver insists the school/service must release their child to their care, the school/service will need to do so."
Canterbury Primary Principals Association president Shane Buckner said schools had been waiting for clear guidance on what they were allowed to do in such situations.
But he said letting parents collect children could be tricky.
"It is somewhat surprising, especially if you put yourself back into that lockdown situation where they don't want mass groups around," he said.
Somerfield School principal Denise Torrey said it was good to have the guidelines.
"We just wanted to know were we able to give the kids to their parents or not," she said.
"I can see that there could be problems with [that] but we wanted to know what our legal right was and I guess they are telling us through these guidelines."
She said toileting was a problem for many schools during the 2019 city-wide lockdown.
"We had children using buckets and plastic bags, which was probably more distressing than trying to get to the closest toilet. So I think the ministry has listened to some of the comments on this from whānau and schools," she said.
Torrey said she did not agree that schools should not practice classroom lockdowns with their pupils.
The guidance said practising for violent situations could cause undue fear and anxiety.
Torrey said her school held three drills every term - one each for fire, earthquake and lockdown - and they were a good way to spot any flaws in its planning.
Canterbury West Coast Secondary Principals Association president Phil Holstein was part of a working group that considered how schools handled the Christchurch lockdown and which led to the ministry's guidance.
"A lot of issues became apparent and one of the big things was that parents wanted to make sure that their child was safe and a good number turned up to schools and also expected they could take their child away," he said.
"Schools in their position weren't sure what to do, because we were told that we were required to keep all our students on site and inside, so there was tension."
Holstein said it was now clear that schools had to let parents collect children, but in a controlled manner.
He said schools needed to ensure students knew what to do during an emergency lockdown and his school did that in a manner that did not cause anxiety.
"I think you can keep it at a very low level," he said.
Holstein said it was sad that Christchurch had experienced both the mosque terror attacks last year and the 2011 earthquake, and their experiences would help ensure other schools were better prepared for emergencies.