The primary teacher shortage will be at disaster point by 2030 given the latest student number projections, the teachers union the new Zealand Educational Institute NZEI says.
Ministry of Education figures released to NZEI show New Zealand will have an extra 40,000 primary school students by 2030, requiring up to 1815 additional teachers.
The institute says the new figures are a worrying addition to a growing crisis, in which schools are struggling to maintain enough teachers for the current student numbers.
"At the current rate of churn, we are swiftly moving from a crisis to a disaster," said NZEI president Lynda Stuart.
Student numbers for teacher training have plunged by 40 per cent in the past five years, a bubble of baby boomers is nearing retirement, and the huge workload and low pay is pushing many out of the profession within a few years of graduating, she said.
"And that's before we factor in an extra 40,000 children."
Exact numbers of the required full-time equivalent teachers are difficult to calculate because there are differing teacher-student ratios at different year levels, the institute said.
However, at a ratio of 1:26, an extra 1535 teachers will be needed and at a ratio of 1:22, an extra 1815 teachers are needed, it said.
The Government has announced it is going to build 12 more schools in Auckland - 10 of those primary schools - but NZEI said they may be "ghost schools" unless the crisis in teaching is addressed.
In Auckland alone, the ministry has said that there will be 38,000 more primary and secondary students by 2030.
Wellington principals are reporting difficulty in filling teacher roles, the institute said.
Ms Stuart said it was time for the Government to act on the growing consensus for investing in education, improving teacher numbers and teacher pay.
"Our public opinion polling continues to show strong support for taxpayer dollars being spent on education, and the public supports a significant pay increase for educators.
"And now with the National Party's u-turn on school policy, including class size and teacher pay, there is simply no opposition to addressing the crisis in education."
Primary teacher and principal members of NZEI are currently voting in a secret online ballot on whether to extend the current planned strike on August 15 from three hours to a full day.
Voting closes on Tuesday night, with results to be announced on Wednesday.
Addressing teacher supply is a priority- Ellen MacGregor-Reid, Ministry of Education
The Ministry of Education says it's surprised by NZEI's claim New Zealand's teacher shortage is heading towards disaster point by 2030.
"We are aware of the projections that's why in Budget 2018, $370 million was set aside to fund 1500 more teacher places by 2021 to meet population growth," said Ellen MacGregor-Reid, Deputy Secretary of Early Learning and Student Achievement.
Addressing teacher supply is a priority, Ms MacGregor-Reid said.
Last year the Education Minister announced a $9.5 million teacher supply package to address immediate pressures by supporting more graduates into permanent teaching positions, supporting experienced teachers back into the profession and recruiting new graduates into teaching, she said.
A further $20 million was provided in Budget 2018 to continue to fund these initiatives over the next four years.
"To attract people to the teaching profession we have proposed increasing salaries for new teachers in the current bargaining round," Ms MacGregor-Reid said.
The ministry has offered a cumulative increase of 14.7 per cent for graduates with a teaching degree ($47,980 to $55,030) over three years and a 14.2 per cent cumulative increase for graduates with a subject degree and graduate teaching diploma ($49,588 to $56, 638) over three years.
"That means the starting salary for qualified teachers would be $50,280, increasing to $55,030 in 2020," she said.
"We’re also working with the sector to develop a workforce strategy, which includes improving recruitment and retention - the first education workforce strategy in 30 years."