The teacher's name, plus that of the school, remain suppressed until a further hearing.
His teaching certificate is under interim suspension and he is no longer working. The school does not support the continued suppression.
Sitting before Judge Anne Kiernan, who heard the case alone last week, the court heard how the boy, now aged 17, had liked and respected the teacher before the incident.
Afterwards, he was left shocked and "never wanted to speak of it again", a friend said.
The boy gave evidence sitting just metres from the man. He was grilled extensively on the details by defence lawyer Richard Earwaker, who accused him of "making up a story for his mates".
However, the judge found the boy was a truthful witness.
Others to give evidence included the school principal, a teacher, a teacher aide, an IT expert and police.
The school's IT head said a server log showed the teacher had been accessing Tumblr sites with various URLs.
The defence disputes the allegation that the act took place in public and has indicated it will argue the teacher had a reasonable expectation of privacy at a further hearing. This is despite a previous ruling saying it could be considered a public place.
The man will reappear on May 22.