Students can dye their hair but they are expected to have it a "natural" colour, so no pink, blue or green. And it can only be one colour.
The school made more allowance for long hair, Mr Kaua said.
"For cultural reasons there are some male students who prefer to wear their hair long."
He said it was made clear to new students when they enrolled what the school expected of them, including standards for appearance.
But he was uncomfortable with the court's decision.
"Rules are rules, and they're there for a reason. This could open the gates to all kinds of court action."
Richard McMillan, principal of Taihape Area School, said the court decision presented an interesting dilemma for schools.
"It's not really just about the hair; it's possible that if parents don't like any school rule they can challenge it," he said.
Mr McMillan said hair "was not an issue" at his school.
"We're more concerned with teaching and learning. There are a few boys who have long hair, but we're relaxed about it."
Mr McMillan said any boys with long hair normally got their hair cut of their own accord once the rugby season started.
Commenting on Lucan's case, psychologist Nigel Latta said parents were increasingly bringing lawyers in to work out issues at schools, a practice he said was wrong.
Others in the education sector have expressed concern that the case may spark further such legal challenges to school rules.