A former deputy principal of an Ipswich school will spend four months behind bars after pleading guilty to child sex abuse charges.

A former Queensland deputy school principal has been jailed for four months for child sex abuse offences committed 30 years ago.

Paul Wruck, 56, was sentenced in the Brisbane District Court on Friday to 18 months’ jail, suspended after four months, for two counts of unlawful or indecent treatment of a boy under the age of 14.

Wruck, who pleaded guilty, resigned as a deputy principal at St Mary’s College in Ipswich when he was charged in October this year.

He was volunteering as a fatherly mentor for his 13-year-old schoolboy victim in Brisbane in 1982 and 1983 when the offences occurred.

Justice Brian Devereaux said Wruck at the time had never had a sexual relationship and lived a “monastic lifestyle” while training to be a Catholic brother.

He said Wruck had since become a highly respected teacher, was the father of an Olympic discus thrower and had been assessed by a psychiatrist as not being a pedophile.

Justice Devereaux said the abuse had had a lifelong effect on the victim and Wruck.

“I even wonder whether a sense of guilt has driven your good conduct,” he said.

But the judge said Wruck’s actions were unforgivable.

“The child was delivered to you … for guidance,” Justice Devereaux said.

The victim told the court Wruck’s actions had taken his innocence and dignity, leaving him with guilt, remorse and confusion.

He had blamed his parents for putting him under Wruck’s care and was still estranged from them.

In his 20s and 30s the victim was addicted to alcohol and for a long time he was unable to have intimate relations without having painful flashbacks, the court was told.

“Although 30 years have passed since the abuse stopped, the pain and suffering has not diminished,” the victim said in an impact statement.

“It has been a passenger with me since 1983 and continues to negatively influence my life.”

Wruck is set to be released early next year.