The secondary school teachers union says most of its members earn over $100,000 a year

Tens of thousands of teachers are joining other workers in health and education, and stopping work on Thursday.

Public Service Minister Judith Collins is criticising the major strike, saying the Government already made generous offers to the members.

PPTA President Chris Abercrombie says two-thirds of teachers are at the top of the pay scale which has a base salary of $103,000.