An affair between a teacher and a pupil was uncovered when the boy's parents saw incriminating video footage on his mobile phone, a court has been told.
Birmingham teacher Rebecca Poole, 26, allegedly had sex with the 15-year-old in her car on up to seven occasions.
Prosecutors said the boy filmed a further sex act "for posterity or for bragging rights".
Ms Poole, of May Lane, Hollywood, denies three counts of sexual activity with a child.
Sally Hancox, prosecuting, told Birmingham Crown Court the relationship grew from being close and flirty to being inappropriate and unlawful in the autumn term of 2005.
While some would see it as every schoolboy's fantasy to have that kind of attention from a young, attractive member of staff, the relationship involved a serious abuse of trust, she added.
The court heard the boy "let it be known" the relationship was taking place, and as a result his parents became aware something was going on.
When they questioned him and found the video footage on his mobile phone, they contacted the police.
During interviews, Ms Poole, who also denies one charge of abuse of trust with a child, denied having sexual relations with the teenager, but then admitted one incident occurred "under duress".
Ms Hancox said Ms Poole told police the teenager had held a screwdriver to the back of her head but said that it was not visible in the video.
The trial continues