Wayne Wilton posted that the four, along with a large number of old boys, had been trying to get the Dilworth Trust Board to acknowledge the ethnic imbalance and "take steps to redress the situation".
"They have done this quietly and respectfully, always mindful that there are those who would seek to portray their concerns as racism...," he wrote.
He described the suspensions as "an outrage" which had caused the suspended association members "great personal distress" and made public a matter they had been at pains to keep quiet - namely, their concerns about the "current ethnic imbalance of the Dilworth School roll".
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.
Maori make up 20.2 per cent of the student population, Pasifika boys 44.3 per cent, European 19.7 per cent, Asian 10.4 per cent and 5.4 per cent of students are listed as "other".
Dilworth Trust Board chairman Jon Wain said the board rejected allegations of ethnic imbalance.
"The Board will continue to observe the Founder's wishes as expressed in the Will by granting scholarships to applicants from straitened circumstances, with no consideration to race or ethnicity," he posted on social media.
"The Board rejects recent allegations that it has acted contrary to the terms of the Will, and is disappointed that recent events have detracted from the excellent work done by the school to foster an all inclusive, multi-cultural learning environment."
He said the school had transformed the lives of generations of young men whose circumstances meant they needed a helping hand in life - especially in their education.
"The Board and management believe that the school's success is derived in part from the rich cultural diversity of the students. We are saddened that in this modern world this would even be contested."
Attempts to reach the four suspended men and school officials were unsuccessful tonight.
Labour's education spokesman Chris Hipkins said the allegations by the suspended association members were "unhelpful".
"A school like Dilworth which is set up to help student from disadvantaged backgrounds is clearly going to have a disproportionate number of Maori and Pasifika because the reality of our current society make up is they're more likely to come from disadvantaged backgrounds."