The former head of a prestigious Perth preparatory school has broken down at a royal commission hearing and apologised for allowing a predatory teacher to sexually abuse his students.
The man, identified only as YK to protect the students' privacy, said he tried to monitor the teacher after receiving complaints from his colleagues about inappropriate behaviour but did not remove him from the classroom because he did not believe he had the evidence to do so.
The Royal Commission into Institutional Responses to Child Sexual Abuse has heard that the teacher, identified as YJ, was convicted of molesting five students between 1999 and 2008.
YK, who ran the primary division of the school from 2000 to 2009, said that when he received a four-page letter from a female teacher in 2001 detailing concerns about YJ, he did not consider it "formal" enough to act on.
"With reflection, and with the benefit of hindsight, I realise and know that if I had my time again, and faced with the same situation, I would have acted differently and in a more decisive manner when dealing with the letter I received from (the female teacher) in December 2001," he said.
"Given that (the female teacher) did not make a formal complaint and requested complete confidentiality, I failed to act decisively when provided with that letter.
"I deeply regret that I did not follow up and conduct further investigations or communicate that letter to the headmaster of the school at the relevant time.
"I made an error of judgment. I live with that on a daily basis. I deeply regret that I failed to take more proactive action in response to that. I sincerely and genuinely regret the pain and suffering that the victims have experienced as a result of the misconduct of YJ.
"I am at heart a good person, who made the wrong decision which unfortunately affected the lives of others in ways that I could never have imagined and I have to live with that for the rest of my life."
He said that subsequent to the female teacher's letter, he tried to be in and around YJ's classroom as much as possible.
"I closely shadowed him at school functions, swimming carnivals and school camps," he said.
"I did not observe any inappropriate physical contact between YJ and the children at school functions and did not come across anything untoward.
"Hindsight is a wonderful thing. I didn't believe I had any cause of YJ doing anything of a sexual nature at all."
The inquiry continues.