Schools are being urged to adopt gender-neutral uniforms as part of wider efforts to ensure children with diverse gender identities and sexualities feel welcome.
The Post Primary Teachers Association (PPTA) said students should be able to choose which uniform version to wear regardless of gender, and schools should also provide safe toilets and changing facilities and inclusive sports practices.
The union's rainbow taskforce convenor, Shawn Cooper, said schools needed safe and affirming practices to help students thrive.
"Students with diverse sexualities and gender identities face many challenges at school which routinely distract from their learning. Inappropriate toilet and changing room facilities and restrictive uniform regulations unnecessarily exacerbate stress and anxiety," he said.
Mr Cooper said with regard to uniforms, schools should set out the uniform options and then leave it to the students to choose from those options.
"We've already got some schools that have taken the lead on this and they're finding that it's really been great for their students," he said.
"It takes a lot less bravery to wear the uniform that matches your identity than it does to go before a board of trustees and ask for permission to wear a uniform that matches your gender identity because it's not currently on offer."
InsideOUT national coordinator Tabby Besley said many students would benefit from these kinds of improvements in schools.
"Four out of every 100 students in New Zealand secondary schools are identifying as transgender or questioning their gender, so it's a really important option for them to be able to express who they are and feel comfortable."
Toni Duder from the LGBTIQ support organisation Rainbow Youth said gender-neutral uniforms were incredibly important but few schools had them.
"One of the things that schools have a duty to do is make sure that all of the young people can learn in an affirming environment," she said.
Ms Duder said a lot of schools thought they provided gender diversity by talking about it in health lessons.
But she said schools should be aiming for a full culture change.
"That just doesn't happen in one lesson covering the basics of gender and sexuality. You really need to model it throughout your whole school.
"So that's making sure that you're showing visibility in your English classrooms with the texts you read or in your maths classrooms with the problems, that you're including same-sex couples or people of diverse backgrounds."
Secondary Principals Association president Mike Williams said many schools were quietly allowing children to wear whatever uniform suited them best.
"Each school in their own way has grappled with problems like this in their own way. So there are many schools where this is not news, this has been happening for a long time," he said.
Mr Williams said schools had a responsibility to ensure all their students felt safe and supported, so they could not ignore those with diverse genders and sexualities.