Davis said he was assured today, by the principal of the school's 200-pupil Maori language immersion unit, that the incident would not have occurred had he been there.
Students and whanau had been contacted regarding the costumes.
"Had the Tumuaki - the principal of the Maori immersion unit - been there he assures me he would have required the costumes to have been removed."
Davis said the school's mission statement was that: "All students and staff, inspired by a love of learning, are challenged to discover and develop their unique personal strengths so that they are well equipped to share in the building of a just and sustainable society.
"This behaviour does not support that at all," he said.
"We don't condone it in any way."
Davis said staff identified the students today, and they would be spoken to "about what a very, very poor choice they made".
"We'll try and emphasise the significance of that to them."
He said the students attending the contest were accompanied by three teachers and a "large supporting group of parents."
He was unsure if any teachers were present when the photo was taken at a bowling alley.
Davis said that ironically, after the school's performance, he received a letter from the Napier RSA which described the kapa haka group as being "the most magnificent ambassadors on behalf of their school."
"It talks about them being orderly, respectful, extremely well mannered and helpful to all the staff," he said.
"And then something like this happens and you put your head in your hands and think 'oh my goodness'.
"It's like Prince Harry in his bloody Nazi outfit, it is a really, really poor choice."
It's unknown where the students' costumes came from.
The sale of KKK memorabilia and propaganda is "usually prohibited" on Trademe.