When his son started high school, all the painful memories came flooding back.

For David*, that was when his life changed forever, when he was allegedly molested by a former teacher at a well-known Melbourne private school.

"I was worried about my son because of my experience," he said. "I knew I had to deal with it."

The alleged abuse took place when David was a student at Camberwell Grammar School in the 1970s.

As a teacher was tucking the then 12-year-old into bed on school camp, he reached under the blankets and masturbated him. David said he was also abused in the classroom, where the teacher slipped his hand into his pocket.

Police have confirmed that they are now investigating an alleged sexual assault at the Canterbury school. They have interviewed a 73-year-old man from the eastern suburbs who has been released pending further inquiries.

"The investigation continues," a spokeswoman said.

While the alleged perpetrator no longer teaches at Camberwell Grammar School, Fairfax Media can reveal that he is still a registered teacher and volunteers at a children's camp organisation.

Camberwell Grammar principal Paul Hicks said the school had been co-operating with police.

"Our school will always offer our care, support and assistance to anyone who comes to us with a concern from the past, and we will encourage them to contact the appropriate authorities – including the police," he said.

"As a school, our first priority is for the safety and welfare of all our students, past and present. We take our responsibility for the safety of students in our care very seriously, and we are constantly vigilant in taking steps to protect them."

Another former student said that when he was at school, another boy confided in him that he had been abused by the same teacher.

David left his family and job behind in the UK earlier this year to travel to Australia to report the alleged abuse.

He is now speaking out because he wants people to understand the devastating impact of sexual abuse on victims and their families.

"This has stayed with me for my entire life. I should have felt safe at school, but I didn't," he said.

The 58-year-old has been diagnosed with chronic depression and struggles to sleep at night.

He became withdrawn after the alleged abuse, and neglected his studies. The aspiring mathematician started wagging school.

He began smoking marijuana when he was 13 and then discovered alcohol.

"I have used just about everything except for heroin," he said. "I did this to numb the pain. I wanted to bury the memories."

David's parents sacrificed a lot to send him to the private school. He said his mother used to work double shifts as a nurse so that she could afford the tuition fees.

This made him reluctant to tell them what had happened – he didn't want to disappoint them.

"I felt an obligation to keep going because of the sacrifices they were making," he said. "I felt that there was an expectation for me to finish school. But it became more and more difficult."

Schools are rolling out programs to encourage students to report abuse. The initiatives come as victims speak out in the wake of a state parliamentary inquiry and the ongoing Royal Commission into Institutional Responses to Child Sexual Abuse.

New laws introduced into State Parliament will force institutions including schools to prove that they took steps to protect children under their care.

They will will reverse the "onus of proof", making it easier for sexual abuse victims to sue for compensation.

From 2017, the Victorian Registration and Qualifications Authority will monitor school compliance with new child-safe standards that are designed to stamp out abuse.

Schools will risk having their registration cancelled or suspended if they don't have policies to manage child abuse risks and respond to allegations.

* Name has been changed

Victorian sexual assault crisis line: 1800 806 292

National child abuse helpline Child Wise: 1800 991 099

National sexual assault helpline 1800RESPECT: 1800 737 732

henrietta.cook@fairfaxmedia.com.au