The strikes start today in Auckland and come after the NZ Education Institute (NZEI) rejected the Government's latest offer worth $700 million over three years.
NZEI president Lynda Stuart said the union decided to reject the offer because it felt the Government did not address calls for lower class sizes.
"The question is: will this address the crisis in education and the teacher shortage?
"What we asked for had children at the heart - for example more time to teach and smaller class sizes. This is something that our members now need to decide."
However, the latest rejection shows the union doesn't have the interests of students or teachers at heart, ACT leader David Seymour claims.
"It is breathtaking arrogance for NZEI to think that its meeting room bookings are more important than hundreds of thousands of kids," he said.
"Teachers unions have already shown just how self-serving they can be by rejecting innovative charter schools because they don't use union contracts."
Seymour said New Zealand's children and teachers would be better off without the union, stating the rejection as a clear example of why the union is out of date.
"The vast majority of teachers want to be in the classroom helping our kids learn," Seymour said.
"Parents and families across the country will now be scrambling to make plans for their children while NZEI holds the country to ransom."