A Rotorua school principal says it is almost impossible to find a good relief teacher right now.
Brent Griffin, principal of Western Heights Primary School, said there were few qualified teachers available to step in when a staff member was absent.
"The supply in Rotorua is very low at the moment," he said.
"There are just not enough around."
Mr Griffin was unsure of the reason, but said it could be because of a relatively transient population and rules for relief teachers' registration.
Teachers were sometimes required to pay for a refresher course to continue teaching if they had not held a permanent or fixed-term position in the previous six years.
This applied to those with provisional registration, meaning that they had not held a more permanent teaching position in New Zealand for at least two years.
The Teacher Education Refresher (TER) course cost about $4000 and took 12 weeks to complete.
Education Council spokesman Martin Deakin said not all relief teachers were required to take the course and it "depends on their individual case".
The Council hoped to extend a limited induction and mentoring programme to all relief teachers soon so they would not have to undertake the TER course.
Mr Griffin said another issue was the suitability of the few staff available.
"I would question the quality of the relievers available at the moment."
He said it could be difficult to find fixed-term teachers, who were sometimes needed to cover maternity leave, because potential applicants were reluctant to move from other areas.
"It's difficult to convince someone to move for something other than a permanent position.
"Last year we had three fantastic relievers, but they took other positions."
Murupara Area School principal Angela Sharples said the changes to criteria made it very difficult for relief teachers to maintain their registration.
"I'm actively looking to support the relievers I do have, but there have been plenty of times this year I haven't been able to get relief teachers in," she said.
"There just physically weren't any."
Mrs Sharples said she'd like to see a scheme put in place for remote and regional schools.
"Our real problem is that we're remote, so we have very few staff applying," she said.
"We need a rural service scheme, it's the only way we can solve these problems for schools like ours."
Garry de Thierry, principal at Rotorua Intermediate School, said relief teachers did an invaluable job in the education system.
"Some days we're in a situation where there are no relievers out there."
Mr de Thierry said Rotorua Intermediate had a bank of relievers they used regularly because they had at least one reliever on most days.
"We have about half a dozen who are our regular ones, but they have diminished somewhat," he said.
"We have to be as proactive as possible. Schools have a responsibility to look into ways they can develop and work with their relievers."
Western Heights High School principal Jim Gemmell said he had not had trouble finding suitable staff, but noticed the number of applicants was declining.
There were nine teacher vacancies in Rotorua advertised in the Education Gazette this week, but four of these were permanent positions already filled on a fixed-term basis.
In the wider Bay of Plenty, 42 positions were advertised.
In Auckland, where teacher supply is an acknowledged problem, 432 job vacancies were listed, down from 600 at the beginning of the year.
Labour's education spokesman, Chris Hipkins, said the Government had been failing to train and recruit enough teachers for years.
"National has stripped over $6 million out of the TeachNZ programme, which aims to ensure an adequate supply of teachers in schools and early childhood services."
The Government announced this week that a freeze on new teacher education programmes would end, and it would fund 90 new teachers.
Minister of Education Nikki Kaye said the overall number of teachers in the country was "reasonable" but admitted there was a problem in some areas.
"There is no one measure that will enable the right quality teachers to be in the right place at the right time which is why we have a range of initiatives to address supply pressures."
NZEI president Lynda Stuart said pay was one factor the Government needed to change.
"Unless the modest pay levels of teachers are addressed, it will grow ever harder to attract and retain our best and brightest in teaching."
- Additional reporting by Alice Guy