Some primary school principals want a return to compulsory face mask-wearing as they head into the colder months.
Schools' measures for preventing the spread of Covid-19 are being tested as some regions experience a rise in winter illnesses.
Public health experts have called for more action but the Education Ministry indicated it was not planning any changes.
Whanganui Principals' Association president Linda Ireton said attendance at local schools had almost returned to normal after dipping as low as 50-60 percent at some schools in the first few months of the year.
But she said principals were worried about the months ahead.
"Most of us are concerned with what [the Ministry of] Health has said to us about the potential for an omicron peak in June and also overlayed on top of that, flu and the other ailments that come in winter time. We're looking at that with concern and knowing that it could mean some more interruptions to learning in an already interrupted year," she said.
Some public health experts have called for an explicit plan for protecting schools from Covid through winter, including a requirement for face masks indoors for older children.
Ireton said she would have liked the mask mandate retained and its removal a couple of months ago had prompted some families to keep children home.
"As soon as it's not compulsory then it's really hard for children to go against what they see their peers doing. So we had really great compliance with masks when it was mandatory because it wasn't just that parents were supporting it, which was very important, but it was also that children would see their peers and choose to wear them," she said.
One of the other tools for reducing the spread of Covid in schools was ventilation.
Schools had been told to open doors and windows as required but teachers warned that might not be practical on cold days.
Otago Primary Principals' Association president Vicki Nicholson said her own school, Port Chalmers, was monitoring CO2 levels and opening doors and windows if the levels exceeded 800 parts per million.
"I was in a class the other day, the monitor told us it was up over 1000 [ppm] so we all went 'oops', opened a door, opened another door, opened a window, and within seven minutes it was down at 500. So it is about getting that air going through and as often as you can and yet still keeping the classrooms as warm as you can," she said.
Nicolson said the school did not have an air purifier but she believed that even in chilly Dunedin it could get through winter using windows and doors for ventilation.
However, she wanted better solutions next year.
"We need to put a plan in place for how we're going to sort this in the long-term but in the meantime the portable ventilators the ministry are providing are helping in some spaces, we just need to do a plan so we're not facing this again next year in winter and the year after and the year after," she said.
Principals' Federation president Cherie Taylor-Patel said the ventilation situation needed to be improved next year.
As for masks, she said some principals were happy with the current situation but others wanted a clearer steer from the government.
"My impression is that principals have found this difficult, that there are a range of views out there in the wider community about whether or not students should have to wear masks and definitely they would welcome stronger advice from the Ministry of Health," she said.
Taylor-Patel said facemasks had helped schools restrict the spread of Covid last year and earlier this year.
Secondary Principals' Association president Vaughan Couillault said its members were not calling for changes to the current rules.
"Secondary principals across the country believe that they have got the tools and plans in place now to make a local decision that's right for them. So for example if they wanted to go back to compulsory masks inside or if you wanted to roster home because they had some staffing issues," he said.
He said in recent weeks Covid cases and other illnesses had prompted schools to shut for a few days, introduce mask mandates or roster year groups home due to staff shortages.
Couillault said he was confident many secondary schools could keep air quality within recommended limits without air purifiers.
"The sort of behaviours that public health experts are saying to keep CO2 levels down is open doors and walk outside and in a secondary setting that happens naturally as part of what we do on a 60-minute cycle," he said.
"I have been through all of the rooms I can think of including the ones that I would have thought would be least well ventilated and none of my numbers come anywhere near causing concern."
The Education Ministry said it was confident schools were well placed to continue to plan for and respond to the health and safety of their teachers and students.
It said schools would have their own plans that best met the needs of their students and staff including layers of preventative measures such as hand-washing and good ventilation.
The ministry said it had been working with schools that were worried about air quality in their classrooms.