A SCHOOL athletics coach could lose his job after it was discovered he was convicted of having teenage sex with a 15-year-old girlfriend 32 years ago - when he was 19.

The sex was consensual and the couple was living together at her older sister's home.

But a court this week told the man the law - meant to protect children from sexual predators - was the law.

The offence of unlawful carnal knowledge, to which he had pleaded guilty and been fined $100, made him a "prohibited person" and banned him from working with children in NSW.

His appeal to the Administrative Decisions Tribunal was knocked back because he had been three years older than his "victim" and therefore not entitled to have the ban overturned.

With the laws governing people who work with children under review, the man was one of only 37 people banned from working with juveniles in the past financial year out of more than 212,000 criminal and employment checks carried out by the NSW Commission for Children and Young People.

The man's 1978 conviction was uncovered when he applied for a full-time job as an athletics coach after 12 years working part-time for the same employer. He didn't get the job.

Then his employer told all staff they had to reapply for their positions, even those working part-time.

The man had asked the tribunal to give him leave to appeal the ban so he could work with children.

"As I explained to [the man], the tribunal does not have any discretion in this regard," deputy tribunal president Sigrid Higgins said in her judgment handed down this week.

The man, 51, whose identity has been suppressed along with the school where he has been working, said he had forgotten about the conviction because it was so long ago and thought it had been "spent", or purged from his record because of the time elapsed.

The tribunal obtained the Local Court documents and said the facts seemed to be consistent with what the man said, except for the girl's age - he said she was 16 when it turned out she was really 15.

"The female was a willing partner to each and every act of sexual intercourse she had with the defendant," the Local Court had been told in an agreed statement of facts."

Originally published as Haunted by 32-year-old sex charge