Dilworth School was set up to provide education to underprivileged boys - but just who those boys should be is now at the heart of a debate.

An Auckland private school has been threatened with legal action after four patrons of its old boys' association were suspended when they raised concerns about the school's "ethnic imbalance".

Dilworth School Old Boys' Association member Warren Wilton said the men would be filing papers with the Auckland High Court if they were not reinstated.

The suspended men included former headmaster Murray Wilton, a former housemaster and teacher, Denis Bradburn, a former president of the association John Simpson, and a member of the association's council, Sandy McNeur.

Revelations of the alleged dispute are made in a lengthy post on the Dilworth Old Boys Association's private Facebook page on Tuesday by Warren Wilton, brother of Murray.

Warren Wilton alleged the men were concerned that the over representation of Maori and Polynesian students at the school was against the wishes of the "Founder's Will".

The post highlights that the junior campus - where most boys started their schooling - had the "most apparent" changes in the make up of the student population.

Pasifika boys made up 44.3 per cent of the student population, Maori 20.2 per cent, European 19.7 per cent, Asian 10.4 per cent and 5.4 per cent of students were listed as "other".

Dilworth has traditionally provided schooling for boys from poor backgrounds. It is a boarding school which charges no fees and offers scholarships for some boys.

It is governed by the Dilworth Trustees Act 1902 - which makes no mention of ethnicity in any part of the Act.

It states that the trustees of the Act are "empowered in their absolute discretion to select a pupil" despite whether their parents have been divorced or separated, and any boy qualifies for selection if he is aged over 10 years, "if in any such case in the opinion of the Trustees the selection of the boy as a pupil of the Institute would be in the best interest of the general welfare of the boy".

According to the post made on Tuesday, the ousted men had "been trying to get the Trust Board to acknowledge the ethnic imbalance at Dilworth and to take steps to redress the situation".

"They've done this quietly and respectfully, always mindful that there are those who would seek to portray their concerns as racism, but ultimately without any concessions by the Trust Board."

Warren Wilton said unless the suspensions were lifted, the men would seek a High Court order to force the association to reinstate them, which would "bring unwanted media attention".

No papers have yet been filed in the High Court.

Warren Wilton did not want to comment publicly on the race stoush, but said he was "supportive of my brother".

In a written statement, Murray Wilton said he had no comment to make.

He said the dispute was "expected to be resolved at their Annual General Meeting this month."

A former student, who spoke on condition of anonymity, said most old boys did not agree with the sentiment that there was an ethnic imbalance as the school aimed to provide an education to boys who were underprivileged.

"It does seem that most of the old students don't really agree with the claim that Dilworth has too many Polynesian or Maori students, or anything like that," he said.

"The intent of Dilworth, the reason for it being, is to help underprivileged. The way it's administered is being debated, but the heart of it still stands, it's just you have this group who wants to debate this."

He said it was "a shame" that Murray Wilton had been caught up in a debate about students' ethnicity because he had done so much for the school in the past.

Adam Hiron, a trustee of the association, said it would not be appropriate to comment on the allegations.

Dilworth principal, Donald MacLean, could not be reached for comment.

The Labour Party's education spokesperson Chris Hipkins said he hoped the allegations would not have an effect on how Dilworth chose its students.

"As much as possible our education system needs to provide more, and better opportunities for Maori and Pasifika students who haven't been doing so well in the state education system," he said.