"We sincerely apologise for the harm or offence that has been caused by any students wearing blackfaces on sports day," Ormsby said.
"It is not appropriate, and we consider it to be offensive."
The woman who complained wondered if the pupils understood the significance of their costume choice and how culturally insensitive it was.
"It makes you think about what they're teaching them, our country's history?"
She argued while pupils from other house groups also wore body paint, it was not the same as impersonating people of colour.
"There's a loaded history that comes with dressing like that [in blackface]."
When she visited the school's website yesterday, she was "pretty shocked" to find an image from a previous sports day, understood to be from about eight years ago.
Some pupils were wearing flax skirts, while others held sticks and had leopard-print material wrapped around them.
Ormsby said pupils painted their bodies and faces at every sports day.
However, it was 2021, and while the school had a "traditional heart", it was committed to adapting to "the modern world".
The school planned to work with its wider community on appropriate ways to "build the culture" of its houses and have discussions with its young men about racism.
Pupils involved in any "inappropriate behaviour" would be reprimanded and educated to understand the effects of their actions.
