Tania Tominac, 43, who taught science at St Francis Xavier College in Florey, had been charged with five counts of sexual intercourse with a person under 16, and one count of maintaining a sexual relationship with a person under 16.

The offences were alleged to have occurred in 2005, with the boy claiming Mrs Tominac had sent him numerous text messages and spent hours on the phone with him.

He said the ensuing affair had included oral and anal sex, and an assignation in Mrs Tominac's office.

But Justice Malcolm Gray, who heard the trial in May without a jury, yesterday found Mrs Tominac not guilty on all counts.

Mrs Tominac broke down in tears as the verdict was read out, and sobbed for several minutes.

She made no comment to the media as she left the court.