Teachers and supporters are marching around the country today as part of the first joint strike affecting all state state and intergrated schools.

The march on Queen St in Auckland and to Parliament in Wellington begin at lunchtime and will cause disruption in the cities.

The Ministry of Education says 1424 schools have now notified the ministry that they will be closed today because of the teachers' strike. That's 59 per cent of the 2409 state and integrated schools that have union members.

Many other schools are also believed to have closed but have not notified the ministry. Notification is voluntary.

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Even conservative schools such as Auckland Grammar, which hasn't closed its doors in previous strikes for more than a decade, have closed today in what Grammar headmaster Tim O'Connor described as "as a signal of strong support for the issue".

Westlake Boys' High School headmaster David Ferguson said his board of trustees was unanimous in deciding to close the school, although it will supervise students if they turn up.

"We didn't close the school last time," he said. "We have got sympathy. We understand the issues and we are sympathetic towards what the PPTA [Post Primary Teachers' Association] are trying to do."

The strike is the first by secondary teachers since 2010-11, when industrial action was cut short by the Christchurch earthquake, and the first national joint action ever by unions representing primary, intermediate, secondary and area schools.

The Ministry of Education has offered pay rises of 3 per cent a year for three years, and an extra step at the top of the salary scales, to both the PPTA and the primary teachers' union, the NZ Educational Institute (NZEI). It says the offer would cost taxpayers $1.2 billion over four years.

But members of both unions have rejected the offer because the ministry hasn't offered anything to relieve teachers' workloads by providing more classroom release time.

The NZEI is also unhappy with the pay offer because primary teachers' pay has fallen about 3 per cent behind secondary teachers' pay because of the timing of the two collective agreements. The union wants to restore "pay parity" for all teachers - a principle won through repeated strikes in the 1990s.

Education Minister Chris Hipkins offered the teachers a glimmer of hope in a television interview on Monday night in which he said: "For salaries, there isn't room to move."

PPTA president Jack Boyle said that was a slight change in language suggesting that the Government might find extra money after the strike for non-salary-related workload issues.

But Tina Peters, a Māori language teacher at Carmel College who will speak at the Auckland strike rally at Aotea Square at lunchtime, said she felt betrayed by Hipkins and his Associate Education Minister, Tracey Martin.

"Three years ago [before the last election] I fell for a lot of what they were saying - that 'we understand the crisis, the teacher shortage, the overworked teachers,'" she said.

"That's why I voted for NZ First, because I really like Tracey Martin. And now I feel disappointed."

Peters, who is not related to NZ First leader Winston Peters, although their families both come from Northland, said she struggled to pay rent of $650 a week on the North Shore as a solo mother of an 11-year-old son, and has taken in a Japanese student to make ends meet.

Linda Stewart, an Onehunga stay-at-home mum, said she planned to take her 6-year-old daughter Eliana on the teachers' march up Queen St to Aotea Square to teach her "that people can and must speak out and take action when they want change".

"She is going to learn that fairness goes beyond sharing toys and cutting the cake into equal pieces," she wrote in an open letter to Ministry of Education deputy secretary Ellen MacGregor-Reid.

However Alwyn Poole, who runs two former charter schools that have become state schools with designated character, said his schools would stay "fully staffed and fully operational" because only one of their 58 teachers belonged to a union.

In another article for the Herald, he said teachers' workload was driven by principals demanding "countless and needless meetings and administrative requirement", and would not be solved by national collective negotiations.

"The strikes are missing the correct target and the vast majority of workload issues are not dictated by the contracts," he said.

NZ Initiative economist Dr Eric Crampton suggested the pay issue could be resolved by allowing teachers to pay more to their best teachers, rather than giving blanket pay rises to all teachers which taxpayers could not afford.