Officials have been ordered to draw up guidelines around whether firearms should be allowed in schools.
The government has directed the move after the Manawatu Standard published photos of school children toting assault rifles as part of an army education initiative.
The Defence Force took the guns onto Whakarongo School, near Palmerston North, as part of a leadership programme.
Students, aged nine to 12, were allowed to hold the rifles and practice taking them apart.
Greens Party MP Catherine Delahunty said it was "propaganda" designed to persuade children that the military and guns were cool.
"Guns are not cool ... what is the education value of teaching children how to use assault rifles? It's not acceptable."
Labour Party education spokesperson Chris Hipkins said schools should be gun-free places.
"I don't think that semi-automatic weapons should be in schools. Full stop. And while I think the army had good motivations and good intentions with what they were trying to do, it was entirely the wrong way to capture the kids' imagination."
Education Minister Nikki Kaye said both the Defence Force and Whakarongo School were acting within the law.
However, she has directed officials to draw up guidelines to make clear exactly what is and is not appropriate.
"As a general rule we don't support firearms in schools, but there may be very limited exceptions.
"For instance, we don't want a situation where the Armed Offenders Squad can't turn up to a school if there's a threat. Also I'm aware we have got an Olympic sport in terms of shooting, so there are some schools that are involved in that."
Ms Kaye said she personally was "pretty conservative" about guns in school, but it was now up to ministry officials and the School Trustees Association to establish the rules.
The government expected the guidelines to be in place within three or four months.
The Defence Force turned down an interview request, but in a statement said the visit was approved by the school and all participants were given a safety briefing.
RNZ also asked Whakarongo School for comment, but it has yet to respond.