A student has denied making up a story about seeing his teacher looking at pornography and touching his crotch in the classroom at lunchtime.
The teacher, who has name suppression, denied a charge of doing an indecent act in a public place.
The 17-year-old cannot be named for legal reasons.
He was asked by the teacher's lawyer Richard Earwaker if he had made the story up for his class mates.
The teenager stuck to his story and said he saw his teacher sitting at a desk and touching himself while looking at a computer.
The teenager told the court the classroom door was closed but he got a friend to give him a boost so he could look in the window.
