The primary teachers' union has started legal action over the pay gap between men and women.
It has lodged a claim against the Ministry of Education, saying female workers get up to $10 less an hour than their male counterparts.
The NZEI claim has been made specifically for three education support workers, but it is essentially on behalf of nearly 600 women who work with preschool children in special education.
The Employment Relations Authority has been told they get a lower rate of pay than what male employees with the same or similar skills would be paid.
According to the union, the women get a minimum of $16 an hour, while men would get as much as $26.
