A legal information line for parents has received 30 calls in the past year about teacher misconduct or incompetence.
The service, sponsored by Wellington Law Centre, says parents are much more likely than in the past to speak out when they have a complaint about their children's schooling.
The supervising lawyer of the legal information line, Felicity McNeill, says of the up to 600 calls it receives each year, almost a third concerned student suspensions.
Ms McNeill says parents also complain about teachers' behaviour or the way they teach.
In one case, parents accused a teacher of making a death threat after he told their son that he would kill him if the 14-year-old did not unfold his arms.
The education union, the NZEI, says parents are increasingly quick to act on concerns about their child's schooling.
However, Ms McNeill says though parents are becoming more assertive, many feel overwhelmed by the school system and need guidance.