The two former students were at Dilworth during the 1970s - RNZ has agreed not to name them.
One of the men said two of his friends were assaulted and he and another boy finally decided to tell a senior staff member what had happened.
That person seemed concerned and took them to see the headmaster who had a completely different reaction.
"The headmaster got very angry and accused us of being disgusting liars and despicable boys and gave us six of the best on the spot for bringing the school into disrepute, and impugning the characters of some of the teachers and leaders."
Even that was not enough to stop him trying to raise the alarm.
The man said he and his schoolmate then went to the media.
"We rang up Truth [newspaper] and told them that there was a [school staff member] at a boys' school molesting boys.
"He asked us what school and we got scared and hung the phone up.
"The next day the journalist rang every boys' school in Auckland, so the headmaster figured out it was us and we got suspended for a week," he said.
Another old boy was threatened with legal action for trying to alert senior staff to the abuse.
The boys from Dilworth he knew had been abused were still in a bad way, and the other former students still thought about what had happened there.
"They were sodomised, made to perform indecent acts, stuff like that."
He was disappointed it had taken so long to see any police action.
"It's 40 years too late. Some of the people aren't around anymore to either get justice or get punished for the collusion.
"It certainly went on before I was there and it went on after I left."
The man said he had spoken to police as part of Operation Beverly, the current investigation into the school.
Sex abuse part of school's culture - ex-student
Another former student of the school claimed everyone knew about the staff who would abuse the boys, which had been going on for years.
"From the moment you arrived at Dilworth, it was almost considered part of the culture.
"It wasn't a great surprise to the boys of my year who had been there for longer than me, they were well versed in it.
"They were very aware that this was how things were at Dilworth, you had certain people identified to you as people to be aware of and to watch out and keep the distance from."
The man said his best friend was sexually abused by one of the main culprits.
"We had seen a film of children in Africa who had a dietary deficiency, and the result for these children was that they got bad swollen stomachs as a side effect of their malnutrition.
"My friend told me that he was [with the man] and that he wanted to physically check him to make sure that he didn't have this malnutrition, which involved physically touching him in the stomach and in the area of the genitals.
"I think it was like trousers off. I need to inspect you to make sure that you don't have this."
His friend reported it to senior staff but was threatened with expulsion, he said.
The abuse had a life-long and damaging effect on the boys he knew, and there were countless others who were impacted by it.
Prep school 'hotbed of abuse'
The worst of it had happened to boys while they were in the Dilworth prep school, aged seven, eight, or nine years old.
"A lot of my friends have been there since the age of seven.
"From what I learned and heard from my friends who have gone through prep at Dilworth, that was the hotbed of abuse.
"A lot of this stuff happened while they were in prep, a lot of my friends who've been abused, it had happened to them early."
The man, now living in Australia, said he was shocked to find out, that nearly four decades on, the events of the 1970s were only just coming out.
"The way they've treated these people and denied it and blamed the victim and covered these perpetrators up and then eventually if they were ever exposed to send them on their way to other schools and other communities in New Zealand."
He was saddened and angry Dilworth School had knowingly protected themselves and not the boys for all these years.
"They had a good network of what the hell was going on in that place, and to say that for 30 to 40 years that these people are unaware it beggars belief," the man said.
Despite the police investigation, he thought it was unlikely his friends who were abused would find closure.
"I think it's gone on for too long and the damage has been done."
School's response
Dilworth School said it had previously reported allegations of sexual abuse to the police.
In a statement, Dilworth Trust Board chair Aaron Snodgrass said he was unable to comment on the specifics of these charges while the matters were before the court.
"Dilworth has, both in the past and today, reported allegations of sexual abuse to the police, some resulting in convictions."
