Principals warn the teacher shortage in some regions is the worst they have ever seen as schools reopen for the third term.

They warned RNZ that some schools are likely to find themselves with so few teachers they will have to ask children to stay home, a situation that happened last term in several Auckland schools.

They say the problem is especially bad in Auckland, Northland, and the West Coast of the South Island.

Ardmore School principal Brigid Peterson says she spent all of term two unsuccessfully trying to fill a vacancy.

"I advertised the role three times and was about to do it a fourth, the only applicants I was getting were mainly offshore. I haven't had a New Zealand applicant until my latest round, which I've just completed."

Peterson says she hired the New Zealand applicant but for all of term two she had to work as a classroom teacher on top of her job as principal.

At Point Chevalier School Rangi-mata-rau, principal Stephen Lethbridge says he had two vacancies for jobs starting this term, one of which he filled with an overseas-trained teacher.

"The other position, we didn't have anyone that stood out for us as being a suitable applicant. So we had to convince a retired teacher to come out of retirement and work full-time for a half-year and she agreed to do that, but we can't keep doing that in schools."

The West Coast of the South Island haa always had trouble attracting teachers but Nicola Minehan from the region's primary principals' association says the situation is worse than ever.

"Probably 30 per cent of our schools have positions where they've got relievers filling them simply because they don't want to teach full-time. We've got a couple of schools that have advertised and advertised three times, four times and the only applicants they've had are overseas teachers who are not compatible."

In Northland, Pat Newman from the Tai Tokerau Principals' Association says job advertisements sometimes attracted no applications and schools have unfilled vacancies.

"In many cases you're lucky to get one application. And that's because we've stripped all the incentives off going out to work in isolated areas."

Auckland Primary Principals' Association president Kyle Brewerton says hundreds of teachers have left the region and there are not enough new teachers to replace them.

"We just simply do not have the people to put in front of children. There's been a few instances toward the end of last term where parents were in fact asked to come and get their children because there was no one to supervise them for the day."

Brewerton says that scenario is likely to recur this term unless there are significant improvements.

One Auckland principal, who asked not to be identified, says their school is in "a staffing crisis". Another says they had four teaching roles with temporary cover and the situation is causing "increasing stress".

Auckland Secondary Principals' Association president Greg Pierce said the city's high schools had an unusually high number of unfilled vacancies.

"A regional group of principals, 17 in number from around Auckland, had a meeting the other day and they found out that among the 17 schools there were 37 vacancies, which is really unusual for mid-year."

He says more teachers are leaving to work in other countries, especially Australia where pay rates are higher.

Pierce says large secondary schools have become good at covering the gaps in their staffing so students did not miss out, and that is masking the severity of the problem.

-John Gerritsen/RNZ.