The government can relieve the teacher shortage by increasing teachers' pay and reducing their workloads, the unions for primary and secondary school teachers say.
The Post Primary Teachers' Association and the Educational Institute are preparing for collective agreement negotiations next year and both unions were holding their annual conferences this week.
The president of the PPTA, Jack Boyle, told RNZ the big issue for its members was that there were simply too few teachers.
"We've got a major issue around a shortage of teachers, not just in Auckland, not just in certain subjects, but across the board," he said.
Mr Boyle said pay rates and workloads were part of the problem.
"Remuneration for coming into the profession is insufficient to attract people.
"We've got the lowest levels of trainee teachers in over a decade and then on the retention side we've got large numbers, 20 percent, who are over 60 and they are leaving and what we're seeing is that that decline is steepening."
The president of the Educational Institute, Lynda Stuart, said pay and workloads were also big problems for her union's members.
"They've got those challenging behaviours in their classroom and not a lot of support for that, but there's the increasing demands of paperwork, administration, assessment, national standards is coming up again and again again. They've just had enough basically."
Ms Stuart said the union would try and address the problems when primary teachers' and principals' collective agreements were renegotiated with the Education Ministry next year.
She said the teacher shortage should help strengthen the union's case.
"We've got a teacher shortage because people are not being attracted into teaching, and we're also not retaining people in the profession," Ms Stuart said.
"We heard from young teachers just before who were saying really [they] don't know if [they] can stay in this profession simply because it is so hard and actually [they] are really struggling to make ends meet."
Meanwhile, PPTA members also discussed problems with the NCEA, modern classrooms, and the government's flagship communities of learning scheme, which pays some teachers and principals more to lead changes in groups of schools.
They warned that communities of learning were being rushed and their potential could be missed, and that the NCEA was causing too much work for both teachers and students.
The union's junior vice-president, Melanie Webber, said teachers wanted more help so they could make the most of the new style of classroom being built in many schools.
She said the rooms were open-plan classroom with smaller rooms for group work and teachers were expected to use different methods of teaching in the new spaces.
"There's very little research into how this actually works in schools, what it looks like, what it looks like in a New Zealand context. Currently each school is reinventing the wheel on it," Ms Webber said.
"We need funding from the ministry so that teachers have the time and the funding to do it."