The Race Relations Commissioner is calling for schools to have more progressive uniform policies, taking into account the wide range of cultures and values within the student population.
The Human Rights Commission created a uniform guide for schools to use and says it will help reduce racism and bullying.
It includes calling for schools to be more accepting of students having tā moko or wearing pounamu.
Race Relations Commissioner Meng Foon told Morning Report there had never been a guide before.
He said school boards needed to embrace diversity.
"We really want to encourage schools to create the environment for children to be safe, to be respected, to be valued, so they can strive and thrive as well."
Lots of schools had progressive uniform policies, he said.
He gave examples of some schools allowing girls to wear trousers, some adapting their uniforms for Muslim students and others allowing students to wear a uniform that aligned with their gender identity.
The Human Rights Commission said the guide recognises Māori tino rangatiratanga and oritetanga, affirming the right for Māori to self-determination over themselves and their taonga and ensuring Māori status symbols are given the same standing as Pākehā status symbols.
"Definitely Māori children should be allowed to express their culture in the way they wish to," Foon said.
New Zealand's school attendance statistics were "very bad", he said.
"Only about 55 percent of our children go to school on a weekly, daily basis and bullying is very high - 40 percent in schools... so anything that will help our children be safe in school, embracing culture, embracing their values, respecting them and really attendance is really important."
Everybody had human rights, he said, but it was up to schools to ultimately decide on their uniform policy as it was not mandatory but a guideline.
The guide was created after consultation with students and teachers from 11 schools around the country.