Auckland principals are worried they will have to use teacher aides in place of registered teachers next year because they can't find staff.
The president of the Auckland Primary Principals' Association, Kevin Bush, said one school had already been forced to do that in a room shared by three classes of children this year.
"Earlier this year there was a school that couldn't get a third Year 7-8 teacher so had to combine the three classes and put two teachers in there with a teacher aide," Mr Bush said.
Mr Bush said it would not be a common situation and would only be possible in situations where the teacher aide was working in the same room as at least one registered teacher.
"It is definitely going to be an option that principals are going to explore," he said.
"We are staring down the barrel of a teacher crisis and we need to consider everything that comes across the table."
Mr Bush said the association had asked the government to pay for teacher aides who were filling the roles of registered teachers.
He said it was not fair to expect schools to pay for such staff from their operational funding.
Lynda Stuart, president of the teacher union, the Educational Institute, said the government should not encourage the practice.
"That's certainly not an optimal situation and we shouldn't be encouraging that to happen," she said.
Ms Stuart said teacher aides had good skills for working with children with special needs, but they were not trained teachers.
Meanwhile, principals welcomed the government's $9.5 million package of initiatives aimed at alleviating the teacher shortage, but said it would probably have little impact on their immediate staffing problems.
The package includes an extension of a voluntary bonding scheme for beginner teachers working in decile one and isolated schools; to Auckland schools in deciles two and three; and nationally for teachers of science, technology, maths and te reo Māori.
However, it limited payments to the teachers to $10,500 after three years. New teachers who stay in decile one and isolated schools were eligible for further payments of $3500 after four and five years at their school.
Auckland Secondary Principals' Association president James Thomas said the package would not make much difference to the crisis schools were facing for the start of 2018.
"What we really need now is to get talking about, in the medium and long term, how do we address the issue that there just aren't enough quality teachers available in New Zealand to teach our kids?" he said.
Mr Thomas said the voluntary bonding scheme should have been extended not just to decile two and three schools in Auckland but to all of the city's schools.