The man, now in his 50s, came forward after Fairfax Media reported on Monday that school heads sent out a letter paying tribute to former teacher Christopher Howell's "extraordinary legacy".

"I've never been more disgusted with something than that letter," John*, who cannot be named for legal reasons, said.

"The vision of Howell was enough to make me sick, but what the school was saying about him; it was a lie and the school knew it was a lie and it protected him.

"The school has broken faith with every parent, with every child."

Christopher Howell was a teacher at the exclusive Melbourne private school for more than 40 years. He took his own life in January 2016, three days before his first court appearance on one count of indecently assaulting a student in the 1960s. He had retired in 2009 as the acting head of the senior school and was still involved with the school, but withdrew when he was charged in November 2015.

On the day of the January 29 court appearance, Trinity headmaster Michael Davies and his deputy Rohan Brown sent a letter to the school community in tribute.

"To many, including those penning this letter, Chris Howell was, is and always will be the best educator we have known. He was a hero to many who worked with him and alongside him," it read.

The letter caused deep divides within the Anglican school. Several former students who contacted Fairfax Media said they made complaints to the headmaster and both the president and treasurer of the Old Boys board resigned in disgust. They claimed the heads tried to ban the board from debating the handling of the complaint and subsequent letter.

"There can be no winners out of this horrid situation, not least the victim(s) of sexual abuse who may have had to experience the displeasure of reading the Headmaster's letter," former treasurer Thomas Hudson wrote in his resignation letter obtained by Fairfax Media.

The first time John was aware of the letter was when he read it in the paper on Monday having left the school in 1975 following the alleged abuse.

"I felt on Monday exactly as I felt after it had happened. I felt dishonoured. I felt ill," he said.

"Everything came back to me. Everything."

John said he was sexually assaulted twice by the teacher when he was 15 and a boarder at Trinity. John claimed Mr Howell tried to force his penis into his mouth inside the tent John was sleeping in during a bushwalking trip at Tonimbuk, east of Melbourne, in 1973.

He said he was also assaulted in a storeroom on school grounds about two weeks later.

John said he disclosed the abuse to his father and mother in 1974.

"I remember his [his father's] words. He said 'Son, we love you, we believe you and we'll make this right'," he said.

John claimed he was with his parents when they reported it to boarding master and priest Leslie Wiggins, who was later convicted of indecently assaulting boys in Rosebud. After being told the claims were "nonsense", John said he and his family reported to the headmaster John Leppitt​.

John said Mr Leppitt told his parents: "You need to discipline your child and you need to consider whether or not to keep him in the school."

On their way out of the school, John said they ran into Mr Howell in the corridor. He said his father grabbed Mr Howell by the throat, punched him and said "If you touch him again, I'll kill you". John said the sixth form master in a nearby classroom witnessed the tail-end of the altercation.

John contacted Trinity again following Monday's report and spoke to headmaster Dr Davies, he said.

Dr Davies said in a statement to Fairfax Media that the safety and wellbeing of current and former students was of utmost important.

"If someone makes us aware of an allegation against a former teacher, we immediately offer counselling and support and encourage that person to contact police. Any allegation is treated seriously and with immediacy. Where allegations have been made, we have co-operated fully and openly with the police," he said.

"If abuse was reported in prior years and not acted upon then that is in total contravention of policies and procedures which are now strictly adhered to in the school. 

"The safety and wellbeing of our boys and old boys is our highest priority and we continue to encourage anyone who is upset, has grievances or concerns to contact the school or the relevant authorities."

John has joined two other men in legal action launched by Rightside Legal seeking compensation against the school and Mr Howell's estate.

Another alleged victim has contacted the law firm.

"I'm so angry. But I'm doing this because I have to," John said, encouraging others to come forward.

Another former employee of the school is facing a County Court trial in May. Mark Watson, who cared for boarders, is accused of abusing boys between 1975 and 1978.

* Not his real name.