A boys' home volunteer who raped and sexually assaulted children in his care told one victim "don't worry everybody does it", a Sydney court has heard.
The man, who cannot be named for legal reasons, pleaded guilty to five of 26 historical charges relating to offences in the 1970s and 1980s at numerous foster homes.
He stands trial in the District Court for the remaining 21 charges which allegedly occurred over the same period, including four counts of buggery.
He has admitted sexually assaulting one boy at his parents' home in Sydney's inner west after he was regularly given permission to take children out for day and weekend leave.
After the assault he told the boy "don't worry everybody does it, go have a shower", crown prosecutor Donna Daleo said in her opening address on Wednesday.
Charges were laid after the man spoke twice to an undercover police officer pretending to be one of his victims in February 2018.
During the phone call he admitted a number of sexual assaults, but denied other incidents the police officer raised.
A search of his home found detailed diaries often referencing the name of one of his victims.
The Crown alleges the volunteer committed numerous indecent assaults and counts of buggery against five different boys while working at various foster homes.
One in Sydney's inner west was for boys considered uncontrollable or unable to be looked after by their family.
On his first day there a 12-year-old boy remembers being greeted by a male tutor who rubbed his hand up and down his thigh and told him "It's OK everything will be alright", the court heard.
That night he says he awoke to find the man kneeling beside his bed wearing a robe and no underpants, before he was sexually assaulted.
Another alleged victim hiding underneath his bed covers heard the boy yelping and whimpering.
Both boys climbed out of the bedroom window that night and ran away but were eventually located and brought back to the home.
The bedroom window was subsequently nailed shut.
One of his alleged victims became a "serial absconder" and was moved around different facilities. But the man continued to pay him visits, take him to church and look after him overnight.
Defence lawyer Sharyn Hall says her client has admitted some wrongdoing, but has no recollection of even knowing let lone assaulting two of his alleged victims.
She said there will be no "fancy footwork" in swaying the jury of crimes he admits and in one case accepts he did the wrong thing.
But regarding two alleged victims he "doesn't remember having anything to do with them".
The trial continues.