A Queensland principal who was sacked for not telling police about reports of a teacher molesting students says it is hard to come to terms with how he handled the issue.

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.

Former principal Terence Hayes today accepted that his failure to report the details of the most serious sexual allegations was "grossly incompetent".

He conceded he did not tell the officers about the most serious allegations, including a student's 2007 claim Byrnes put his hand up her skirt.

"It's an oversight that I find very hard to come to terms with. It brings a lot of hurt to me and my family," he said.

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Barrister Andrew Naylor said to Mr Hayes: "If you didn't deliberately refrain from passing that on, it was grossly incompetent on your part not to provide that information".

Mr Hayes responded: "I accept that".

He told the commission he did not inform police about the suspected paedophile because he was "directed" by Catholic Education bosses to refer such matters to them instead.

Jane Needham SC for the Catholic Church disputed that evidence and accused Mr Hayes of lying.

"Is it the case that you will make up stories?" she asked him.

He replied" "No, I am not making up a story".

Ms Needham also asked Mr Hayes about a child safety fact-sheet that principals were given at the time.

"Nothing could be clearer than this fact-sheet requiring you to take this allegation to police, could it?" she asked.

Mr Hayes responded: "No."

Today Mr Hayes also took responsibility for Byrnes being re-hired as a substitute teacher after the allegations had been made.

Mr Hayes said he did not tell the manager who re-hired Byrnes about suspicions he had abused students.

Mr Hayes was asked: "Was it an abrogation of your responsibilities as principal to ensure the safety of students at the primary school?"

He replied: "Yes."

Byrnes continued abusing students as a relief teacher but was jailed in 2010 after a parent went to police.

Further questioning over abuse demonstration

Yesterday, Mr Hayes faced hours of questions over how he dealt with a complaint from a father whose daughter was abused by Byrnes in 2007.

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.

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

This morning he was asked if he believed the child when the allegations were put to him.

"Yes, I didn't doubt the child at all," he said.

He said he thought the demonstration would add "further depth" to the meeting.

Mr Hayes has been excused from giving further evidence.

Two senior staff from the Toowoomba Catholic Diocese office - who were also sacked over the scandal - are the next witnesses scheduled to appear before the commission.

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

The commission 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.