Cameron Peter White, 39, was found guilty of 19 offences on Tuesday after a trial in the Downing Centre District Court.

White, who is bisexual, denied having a sexual relationship with any of the complainants.

He pleaded not guilty to 14 counts of aggravated sexual intercourse of a child between 14 and 16 and three counts of sexual intercourse with a person under care, alleged to have occurred between 2007 and 2013.

During the trial, the prosecution abandoned a further three counts of aggravated sexual intercourse with a person aged between 14 and 16 and one count of aggravated indecency with a person under 16 after it emerged some of the incidents occurred after a complainants' 16th birthday.

But the jury rejected White's claim his relationship with the three students was strictly platonic both during the periods he was their teacher as well as when either he or the students had left the schools.

The male complainant gave evidence that when he and White were both at the same school, they started chatting online after the teacher learnt the 14-year-old gay student had a crush on him.

The pair met in White's car, starting a sexual relationship that would last more than a year.

The young man said White referred to him as "my bitch" and, when he was arrested, police found the student's number in his phone under "biatcha".

One female complainant told the court she lost her virginity to White at his home in Sutherland in Sydney's south after they exchanged messages via Facebook. White had been her year 9 geography teacher at the Georges River College at Peakhurst in 2010.

Giving evidence via videolink, the woman said she was "scared, very tense" and "didn't want to be there".

They met several more times for sex before the student ended the arrangement before school returned in February 2011.

In September 2011, the woman asked him for a reference she needed to apply for a course and he agreed to provide it on the condition they have anal sex, to which she agreed.

White said the claims were "totally false".

In 2015, she and the second female complainant had online conversations in which they revealed to each other that they had lost their virginity to White.

White also denied having sex with this complainant, claiming they were "good mates" and saying his relationship with her was akin to that of "a little sister".

He agreed they regularly went to cafes, movies and restaurants and she had been to his home and in his car, however he described meeting with her on those occasions as like being with "a little sister".

White was a teacher at Woolooware High School from 2004 to 2009, the Peakhurst campus of Georges River College for periods in 2009 to 2011 and the Oatley campus in 2012 and again in 2014 to May 2015, when he was arrested.

White had his bail revoked on Tuesday. He will face a sentencing hearing on July 21.