Principals are appealing to the Ministry of Education to maintain school staffing levels after mid-year roll counts showed some have lost a lot of students.
They said many of the missing children would return after an expected push on attendance next term and as parents became more confident about sending children to school during a pandemic.
Te Tai Tokerau Principals Association first raised the problem with the ministry several months ago and its president Pat Newman said its predictions had proved correct.
"Some schools are 25 to 30 per cent down. Most schools would be at least 10 to 15 [per cent]," he said.
Newman said families were keeping children home for a variety of reasons.
"It's Covid, socio-economics, petrol, getting kids to school, the whole works. Up here, petrol would be one of the biggest costs now that's stopping kids coming back," he said.
He said many schools would have to lay off teachers at the end of the year based on their July roll numbers, but their jobs should be protected.
"Eventually those kids will come back and we may not then have the teachers available," he said.
"There's also the fact that we could use those teachers up here to help our kids that we know are behind."
Waitākere Area Principals Association president Tony Biddick said many schools in the area were missing students.
"We know they're here, we know they're perhaps sometimes skateboarding past the school even, or they've disappeared off our radar but we know they're going to be coming back," he said.
"Staffing calculations are being done at the moment and a lot of schools will have less numbers physically in their school but know that those children are somewhere nearby and sometime in the future going to come back."
He said schools should keep staffing unchanged into next year because children needed more support than ever.
"We've got a whole plethora of pupils who are coming to our schools after two and a half years of Covid with diverse learning needs. The number of these children has just increased exponentially and it's not just in Waitākere. I know talking from my colleagues in Auckland, it's all across Auckland."
Principals Federation president Cherie Taylor-Patel said it was backing the call to protect staffing.
"No one at this time wants to leave good staff members knowing that you probably are going to get those students back [in the] second half of this year," she said.
The ministry has protected schools' staffing in the past.
Last year, it decided to halve any big staff cuts to Auckland schools for 2022 and also minimised cuts to small schools.
It said it would look closely at any cuts for next year.
"While it won't be possible to maintain all staffing and funding entitlements at current levels, we will take a pragmatic approach and work closely with school leaders. Where there is evidence that a drop in roll is temporary, we will support schools to reduce the impact," the ministry said.
It said some changes in schools' rolls would be due to the pandemic but others were because of changes in the local population.