A Christchurch school principal says unless teaching is given a boost there wont be enough teachers for kids in the future.

Up to 3000 Christchurch primary teachers, principals and supporters will join a nationwide strike today, rallying from 11am in the Cathedral Square.

They're calling for a 16 percent pay rise over two years, and improved working conditions.

Halswell School principal Bruce Topham says the government has been given an opportunity to come up with a better offer but hasn't moved.

He says his is a Decile 10 school that normally has an abundance of teachers who want to work there, but a lot of the good ones have been picked up by roles in other schools.