A shortage of college maths and science teachers is being described as a crisis by some secondary principals.
Some schools are having such difficulty finding specialist teachers in the areas, they are persuading retired teachers to return to the classroom.
Others are retraining teachers outside of their speciality.
The director of secondary teacher education at the University of Auckland, Ngaire Hoben, told RNZ's Nine to Noon the situation was fast becoming a crisis.
She said there were three main reasons for the absence of teachers.
"The status of teachers within New Zealand - how teaching is viewed by society - I think that's declined.
"The workload faced by secondary teachers is intense.
"And the pay level is discouraging - and I think a combination of those three things is discouraging people from coming forward - particularly when there are other options available to them."
She said schools were enticing teachers from retirement and getting teachers who were unqualified to teach maths or science - some were PE teachers - to teach the hard to fill roles.
"We could say that physics and chemistry, te reo Maori, technology and to a certain extent English are all becoming what you might call endangered species, with having difficulty in staffing them."
She said the the numbers of people coming forward to teach those subjects had been declining in the past few years - with a large a number of teachers also facing retirement.
Secondary Principals' Association president Sandy Pasley said principals were desperate to get high quality teachers in front of their students.
Mrs Pasley, who is also the principal of Auckland's Baradene College, said in the past aspiring teachers had been able to receive studentships, which meant students were paid to go to university and were bonded to teaching.
She said the pay when she began was the same as a backbencher MP - but that had eroded over the years.
She didn't believe it was feasible to retrain teachers on the spot to fill maths and science positions.
"You haven't got the depth of knowledge to understand the building blocks that you need to give to the students in their secondary school years so they can cope with university study.
"They are specialist subjects and they're subjects that New Zealand needs."
She said previously schools had been attracting teachers from the United Kingdom, but a shortage there was affecting New Zealand too.
That could cost up to $10,000 to pay for a recruiter.
Otahuhu College principal Neil Watson said many would-be physics teachers, in particular, were simply not good enough for the job.
His school took 18 months to fill a senior chemistry role and physics was even harder, he said.
"There's lots of people out there with teaching qualifications and with physics in their degrees but actually good physics teachers are very few and far between."
Ministry of Education enlists recruitment firm, agents
Ministry of Education head of early learning and student achievement Lisa Rogers said there were 33 vacancies nationwide for maths teachers, with similar numbers for science.
She said schools were not alone on the issue.
"We've got a specialist recruiter that's in place and if schools have any issues recruiting any teachers, they can call us, or this recruitment firm, and we're literally scouring the nation and beyond for these teachers."
She said there were a lot of New Zealand trained teachers overseas, and agents were working on enticing those teachers back, but also how to get overseas trained teachers here.
"There's expos in Manchester, Dublin, London and we've got agents physically there, getting teachers into New Zealand."
She said the ministry was "donkey-deep" in solving the issue at every point in the system.
"We're looking at initial teacher education and how we can improve that.
"We're looking at how we can entice those exceptional students... into graduate programs around maths science and technology.
"We're looking at to support teachers once they get into the system, to stay in the system, and have a really great career."