Sydney’s St. Mary’s Cathedral College’s former principal has been found guilty of abusing children during his teaching career at a private school.

David Standen pleaded guilty to 18 child sexual abuse charges, seven of which were of indecent assault against teenage boys. The charges were proven at Downing Centre District Court on Wednesday.

News.com.au reported that the Christian Brother, 66, hung his head while he confessed his crimes committed between 1978 and 1981 when he was a Year 7 dormitory master at a college located in southern NSWs Goulburn. He also admitted to six other child sex abuses, which the court will be considering when he will be presented to be sentenced in April.

Under Judge Martin Blackmore, Standen was also found guilty of 11 more child sex abuses on Monday, after which he confessed his involvement in other seven charges on Wednesday. According to the Sydney Morning Herald, the facts revealed that Standen used to take advantage of being a dorm master. He had a dorm room attached to a bedroom where he used to assault boys on a regular basis.

He abused a student for the first time in 1979. He continued to do that up to 20 times a week, asking the boy to pull down his pants and bend over his knees. Using his hands or belt, he would smack him on the bare bottom.

On his trial on Tuesday, prior to empanelment of the jury, he told the court to “consider his position.” He returned to court on Wednesday and confessed of the remaining crimes he has committed. Standen remained the principal at St. Mary’s from 2000 until his retirement in 2010. He was arrested on August 19, 2014 when he returned to Australia from an overseas trip at Sydney Airport.

Standen is due to be presented to court on April 15.