Primary school teachers and principals have voted for a full day strike.
NZEI members will walk off the job on August 15 - two weeks away.
Lead principal negotiator Louise Green says the decision sends a strong message to the Government that it's time to fix this crisis in teaching.
She says there needs to be better investment in education, and enough teachers for every class.
"A clear majority of both member groups voted in favour of a full day, giving a strong endorsement for collective action," she said in a statement.