The former principal at a Queensland school has told the royal commission into child sexual abuse why a girl and her father were asked to re-enact an encounter with a paedophile teacher.

Teacher Gerard Vincent Byrnes molested 13 female students, all aged between nine and 10, at a Catholic school in Toowoomba in 2007 and 2008.

The Royal Commission into Institutional Responses to Child Sexual Abuse is looking at why Byrnes was allowed to go on offending for more than a year after allegations were first made against him to the school.

Byrnes, the school's child protection contact, pleaded guilty in 2010 to child sex offences, including rape. He carried out all but two of his crimes in the classroom.

Terence Hayes was in charge of the school when Byrnes assaulted the year four students.

In 2007 Mr Hayes arranged a meeting with a female student and her father after the girl had complained about abuse.

The girl was asked to pretend her father was the teacher and "demonstrate" how he abused her.

Barrister Andrew Naylor questioned Mr Hayes about that approach, saying: "Did you have an expectation that KH would invite her father to put his hand up her skirt?"

Mr Hayes said the demonstration was suggested by a student protection officer "to more authenticate what she was saying".

Byrnes continued abusing girls before being jailed in 2010.

The Brisbane hearing has been told many of the assaults could have been prevented if complaints had been handled properly in 2007.

The commission has heard the complaint should have been referred to police under the school's policies, but neither Mr Hayes nor Catholic education officials contacted authorities.

Mr Hayes was sacked over the scandal but was acquitted of failing to comply with mandatory reporting laws.

Earlier today he told the commission he did not follow the reporting policies because he believed the local Catholic Education Office was the "first port of call".

"As per our advice that we'd received at our principals meetings and principals gatherings," he said.

Assistant principal would have 'done things differently'

Megan Wagstaff leaves the royal commission in Brisbane today. ( AAP: Dan Peled )

The assistant principal at the school, Megan Wagstaff, also testified.

In 2007, Ms Wagstaff took a phone call from a mother whose daughter had heard another student say Byrnes had put his hand in her pants.

She told the hearing she referred the parent's concerns about Byrnes to Mr Hayes, but police were not notified and Byrnes continued assaulting students.

She said she believed she would have "done things differently".

She said she would use a child protection form to alert authorities if she was in a similar situation again.

"I would use that form, I would follow that process ... via my principal, I would give it to the police," she said.

Ms Wagstaff said she had not referred to policies in the school's child protection kit at the time, but she consulted a student protection officer.

On Monday, the parents of three of the victims fronted the commission, with one mother saying the school's refusal to act on allegations was "disgusting".

Another mother of an abuse victim said she and other parents were ostracised by the school community after they complained about the abuse and how the school had dealt with their concerns.

Senior education officers from the Toowoomba Catholic diocese are due to appear before the commission this week.