A 2015 PPTA survey found the problem affected secondary schools across New Zealand, which are finding it increasingly difficult to recruit teachers - particularly in subjects such as the sciences, mathematics, technology and te reo Maori.
University of Otago College of Education senior lecturer Dr Chris Linsell believed the shortage was being caused by the increasing number of teachers being lured away by higher paid non-teaching jobs, the large cohort of teachers reaching retirement age, and the lack of teaching graduates coming through to replace them.
Using specialist maths teachers as an example, Dr Linsell said the college of education trained very few of them.
''We've got a major issue because the secondary graduate diploma in teaching programme has been suspended in favour of the masters degree, and this year we started off with two specialist maths teachers, one of whom has dropped out.
''In the past, we were training more specialist maths teachers in the graduate diploma, but still not a large number - typically about five or six.''
Specialist maths teachers are those trained to teach at year 13, NCEA level 3.
Dr Linsell said there was a real danger the shortage could result in pupils not getting the education they needed.
''Because there's such a shortage of maths teachers, we end up with needing to use other teachers - particularly for the junior maths classes in year 9, 10 and 11 - who aren't specialist maths teachers.
''That is more of an issue in the rural schools around Otago.
''In the Dunedin schools, you will always have some excellent, well-qualified teachers in maths up to year 13, who are heads of department, who are able to support teachers for whom maths isn't their specialist subject.
''But that's not necessarily the case in the rural schools.''
Otago Secondary Principals' Association secretary Gordon Wilson agreed it was a significant and widespread issue across Otago, and said schools were doing their best to make sure the shortage did not affect pupil education.
Dr Linsell said a major part of the shortage problem was few secondary school pupils were opting to study for maths degrees at tertiary level.
''I don't believe there are any quick fixes - except one, of course: pay teachers more.
''If you paid teachers the same sort of salary as doctors, the problem would be solved.''
He believed a more realistic solution would be a long-term intervention in the nation's education system.
The College of Education was working with the University of Otago's mathematics department to develop pathways which encouraged more maths graduates to go into secondary teaching, he said.
But he believed the intervention had to go deeper.
Work needed to be done at primary level, to get pupils enjoying maths and wanting to study it at higher levels.
''We're into a whole cycle here that I believe has to be tackled at all levels of the system.''
Ministry of Education student achievement head Dr Graham Stoop said the ministry supported schools that were having difficulty recruiting staff.
The ministry was also responding to the demand for secondary teachers on several fronts.
That included drawing together a sector group to address workforce issues as part of a complete workforce plan; subsidising the cost of recruiting for schools with difficulties finding staff; providing allowances for schools which were hard to staff; and reimbursing relocation costs for teachers.
