The sounds of their sobbing had filled the court room as the former Trinity Grammar School teacher was found guilty by a jury of 22 child sex charges, including eight counts of buggery, on Wednesday.

Futcher's trial had heard distressing details of how he sexually abused six boys, aged between 12 and 15, while he was working as a teacher and swimming coach between 1974 and the early 1980s.

Robert Anderson, 53, who was a student at Trinity and abused when was 12, said he had nearly given up hope that he would ever see Futcher brought before a court.

He said he first told police about the abuse in 1990, and again in 1997, but it was after giving evidence at the Royal Commission into Institutional Responses to Child Sexual Abuse that Futcher was finally charged.

"After so long. I've just been fighting this for so long. It feels exuberant to be finally believed," Mr Anderson said.

"Everyone knew but in the end it comes down to those 12 jury members. They could see the truth."

Futcher, who was in late 20s and early 30s when he committed the abuse, ingratiated himself with the parents of his victims, frequently dropping in to see them after school and on the weekends.

He hand picked students to attend unofficial school camps, where he showed them pornography, encouraged them to skinny dip, made them sleep in his bed and sexually abused them.

Futcher, who had previously taught at Sydney Grammar School and was also boarding master at Knox Grammar School, abused the boys in various places including in the back of his van, in his mother's apartment and in a surf life saving club's toilet cubicle.

He took an explicit photo of one boy and threatened to show his parents.

Now 69, Futcher gave evidence during his nearly month-long trial and adamantly denied all of the charges or that he had a sexual interest in pre-teen boys

"I've always liked the older ladies and when I was a bit predatory I used to go to various wine bars, piano bars, hotels etc. etc. looking for company," Futcher told the court.

The court heard that in 2015, he asked one of his victims to "be forgetful" and said he was "begging" him not to tell police about the abuse. A covert recording also captured Futcher apologising to a victim and telling him he had a "weakness".

Mr Anderson said it had been hard to hear Futcher's denials but not unexpected.

"The lies have been unbelievable but that's how it goes," he said. "We tell the truth, he tells the lies."

The jury, some appearing emotional, delivered guilty verdicts to all counts in the Sydney Downing Centre Court complex.

Futcher's lawyer sought to have his client remain on bail, but this was denied due to the likelihood that he will receive a jail sentence.

Victims and their supporters stood together and watched as two guards led Futcher away to spend his first night in jail.

A sentencing hearing will be held on October 28.