Industrial strife over class sizes is looming after an "emergency summit" of primary teachers' union the NZEI.
President Ian Leckie said principals and teachers would be asked to put class sizes on the agenda for contract negotiations starting in August.
"Parents and teachers are rightly concerned at the impact this decision will have on children's learning."
Education Minister Hekia Parata announced earlier this month that the funding formula for middle-year schools would move to one teacher for every 27.5 children from as low as one to 23.
- The Dominion Post
How excited are you about the 2014 Commonwealth Games?Related story: After the hype, time to let the Games begin