Teacher Nigel Studdart, sacked from Whangarei's Pompallier College for "serious misconduct" after supporting a student protest over comments the principal made over gay parents, wants his job back.
Mr Studdart was sacked last month, three weeks after he was suspended for speaking out against what he called discriminatory comments by the Catholic college principal, Richard Stanton.
He was stood down the same day some students planned a silent protest against Mr Stanton's comments in the school newsletter opposing the Marriage (Definition of Marriage) Amendment Bill.
Mr Studdart's letter from the board of trustees said his teaching practice was not in question but he had been dismissed for serious misconduct.
The science teacher said he would fight the dismissal with the help of his union, taking it all the way to the Employment Court if necessary. He is also looking at making a complaint to the Human Rights Commission.
"This is not about wanting any money [for unjustified dismissal] or a vendetta or anything like that, I just want my job back.
I love my job teaching kids and I think I'm good at it," he said.
"I've got a great relationship with my students and other staff, and this was all down to a difference of opinion with one person at the school."
Mr Studdart said he had been overwhelmed by the level of support over the issue, with constant messages from students and their parents. Dozens of people from around the world have signed an online "reinstate Nigel Studdart" petition.
"I had a card from one parent yesterday [Monday], saying 'Thanks for standing up for what you believe in and teaching the kids to stand up for their opinions as well'. Those are the sorts of things that keep you going."
He said his actions in supporting the students and opposing what he called ill-informed comments on the abilities of gay parents did not equate with serious misconduct.
The school has said it will not comment further on the issue.