For the past 147 years, Otago Girls' High School's uniform has included skirts, kilts, blazers, blouses and even smocks.
But next year, the school will allow its pupils to wear trousers for the first time.
Principal Linda Miller said it was part of the evolution of the school.
"In education, there's far greater recognition of the importance of inclusiveness, and I think this is just another example of how the school is acting in a way to be more inclusive of all of our students."
She said inspiration for the change came from school council prefect Hannah King and board of trustees student representative Sabrina Swerdloff.
"Some of our wonderful students thought this was an appropriate time to broach the subject.
"The girls put together a proposal for the board which was very well reasoned, well researched and well thought out."So the board approved their proposal.
The formal uniform would remain as the kilt and summer skirt, but the pants would be an optional item that pupils could choose to wear, she said.
"Personally, I really like the kilt. It's a lovely uniform. But I want the girls to be comfortable," the principal said.
"Ideally I'd like the girls to be more active and I think having pants will enable them to do things like coming to school on bikes and being more actively involved in things around the school grounds during break times.
"Anything that can promote physical activity in this era, when it is a huge issue for society, is a really good thing."
Sabrina said this was her final year at Otago Girls' High School so she would not benefit from the new uniform option.
"But I'm really excited for the other students who will get to wear them, and I think it will still be really exciting to come back in the future and see other girls wearing them.
"I think it's really important that girls have the option to wear pants, because there is no other part of our society where we force women to wear something or we force women to do something.
"So I think it should be exactly the same at school. It's very archaic to continue making women wear skirts when pants are a normal part of society."
She said it was still too soon to know how popular the new uniform option would be.