NZEI Te Riu Roa and the Post Primary Teachers’ Association (PPTA) voted on the weekend in favour of taking joint strike action on May 29.
Around 50,000 teachers from both primary and secondary schools are expected to participate in the mega-strike.
Both unions previously refused to accept the Government’s latest $1.2 billion pay package offer over four years, citing it wasn’t enough to make teaching a viable career choice.
PPTA president Jack Boyle said it was disappointing that negotiations with the Ministry of Education had stalled, leading teachers to walk off the job.
“We are united in our aspirations. We want every child to leave school with the skills, knowledge and confidence they need to reach their potential,” Boyle said in a statement.
“Teachers do not take strike action lightly. We would rather be with our kids in our classrooms. We want a positive outcome.
“It is hugely disappointing that we have reached this point. We want to work with the Government to agree solutions that make teaching the attractive career it should be.”
The Education Minister Chris Hipkins slammed the strike action however, describing it as “unjustified”.
Hipkins said the Government's $1.2 billion offer for teachers was the largest in a decade.
"It represents more than all of the settlements reached under the previous government put together," Hipkins said in a statement.
"It's one of the largest pay increases on offer across the public sector and is well ahead of what most workers throughout the economy are being offered in terms of pay increases."
Despite the Government's stance, NZEI president Lynda Stuart said teachers had the support of parents and the public.
“The outcome shows teachers and principals are united and resolute in their commitment to getting significantly improved pay, time and support for learning needs,” Stuart said in a press release.
“The offers we have received from the Government have not addressed the issues our profession is facing. They will not turn around the crisis in education that is looming.”
“We know we have enormous support from parents and we ask all New Zealanders to support us in our fight for the future of education in New Zealand.
"Teachers have spoken - they want the Government to find a solution, now. Our children cannot wait and neither can our teachers,” she said.