School principals in Auckland say they are struggling to find enough teachers before classes start next week.
They say the teacher shortage is the worst they've ever seen and in some schools senior managers will have to fill in as teachers.
Otahuhu College is one of the schools that was still looking for teachers before reopening for lessons on Tuesday next week.
"At the moment we are short of two teachers, a maths teacher and an English teacher," the school's principal, Neil Watson, said.
"We've been advertising for the maths teacher since about July last year, so there's real shortage out there of good quality applicants for the positions."
Mr Watson said senior managers might have to teach some classes while the school hunted for staff.
He said Auckland's house prices and traffic problems contributed to the difficulty in finding teachers, but the shortage of maths teachers was nation-wide.
Mr Watson said he was determined to hire top quality teachers and would not settle for second-best because of the shortage.
"We all know from our own experiences at school you get a good teacher in front of you and you're successful. If you have a teacher who's weaker then you go backwards in your learning and our job is to make sure that we do the very best for our students and and for their families."
The president of the Auckland Secondary Principals Association, James Thomas, said three of the six secondary principals he had talked to in the past week were still looking for teachers.
He said that was unusual for this time of year.
Mr Thomas said schools would try to cover classes with teachers who had some experience with the subject in question. For example, using a phys ed (physical education) teacher who had studied science at university to teach some science classes.
However, he said some schools might have to cancel particular subjects or classes altogether.
"There will be some schools that will have to modify the programmes they offer because they do not have quality teachers.
"They'll have to say, 'no, sorry, we cannot teach this course' and then you might have to take it through a virtual learning network or Te Kura, the correspondence school, or they might just say 'it's not available, pick another subject'," he said.
Auckland Primary Principals' Association spokesperson Frances Nelson said the teacher shortage was the worst she had ever seen.
She said some principals still had unfilled teaching vacancies and others were likely to return to school this week to find some of their teachers had accepted jobs at other schools during January.
"It's late in January that principals will hear they are in fact short, so we are all holding our breath and it will get worse as the year continues because our rolls increase into the year and we are very, very concerned about how that is going to play out."
Ms Nelson said there was nothing the government or Education Ministry could do now to help schools with their immediate shortages.
But she hoped they would intervene to prevent the situation worsening.
"We can't go through another year like this," she said.
The Education Ministry's Associate Deputy Secretary, Education Workforce, Sarah Borrell, said it was working hard to support Auckland schools that were finding it difficult to recruit staff.
"In Auckland, schools were phoned in early December and all of those with vacancies were offered specialist recruitment assistance to fill those vacancies.
"Twenty schools took up the offer and listed 44 vacancies, half of those have already been filled and work continues to fill the remainder," she said.
Other initiatives included a recruitment campaign in the UK, a campaign to persuade New Zealand teachers working overseas to return, and scholarships to encourage science and maths graduates to train as teachers this year.
Ms Borrell said many of the solutions were included in a $9 million package of initiatives announced by the government in August last year.
"Although it is still early days, we are beginning to see signs that non-NZ teachers are seriously considering coming here to work and that New Zealand teachers are looking to return," she said.
Ms Borrell said there were 50 primary, 79 secondary, and 19 composite/other teacher vacancies in Auckland in December, figures almost identical to December 2015.