Thousands of secondary students are zipping their lips for the day in a stand against the bullying of gay, lesbian, bisexual and transgender school students.
Charity InsideOUT is calling for action on the situation and has organised a day of silence in protest at such bullying, today.
Event organiser Tabby Besley said research showed bullying of gay, lesbian, bi, and transgender teens was far too common.
"At least half of gay, lesbian, bisexual and transgender students are being bullied on a weekly basis, I think as well over half of them have actually been physically harmed or hit at school because of homophobic bullying, which is really disappointing."
And she said it was a problem that just was not going away.
"There's been no change in this type of bullying in the last decade so the number of people who have been experiencing it on a really regular basis at school hasn't changed, so I think it's quite shocking."
Of the 40 schools participating, Wellington College will be the only boys' school.
One of the organisers there, Kip Cleverley, said the LGBQT community was so invisible there was not really any homophobic bullying, but he wanted to raise awareness.
"At our school there is a lack of visibility for the LBGT community and I think this event is a great way to say 'hey, we do exist at this school, and throughout the country'."
A Wellington High School student said he hoped the day would draw attention to the silence of victims of bullying.
"I have experienced a few instances of bullying here, mostly in my junior years, and honestly I didn't want to speak up about it, but it was my friends who encouraged me to talk to staff about it and actually have it resolved," he said.
Chief Human Rights Commissioner David Rutherford said bullying of gay, lesbian, bisexual and transgender students was a significant problem.
"GLBTI students are at least three times more likely to be bullied than other students, except students with disabilities are at similar levels.
"But it is a very significant problem and in some areas leads to suicidal behaviour and indeed suicide."
Mr Rutherford said schools must make it clear these students are as much a part of their community as anyone else.
"There's no point in trying to deal with bullying by taking a sledge hammer to every incident that happens because the real cause of it lies in the disrespect for difference, and that's the sort of stuff you need to be working on as well - every day in every way you can."
He said that included measures like the gender-neutral uniforms and safe toilets recommended in recently-published sexuality education guidelines for schools.