An English teacher allegedly told a 16-year-old pupil 'I bet you won't be able to keep up with me' before having sex with him in her car.
Emma Ager, 34, from Wales, is also reported to have told the boy that he would be 'a legend' amongst his friends following their trysts.
The relationship came to light after the boy's mother found out her son was getting inappropriate phone calls and texts from Miss Ager and contacted his school – but at the time she had no idea that their contact had become sexual.
Miss Ager is now up before a disciplinary hearing accused of unacceptable professional conduct and falling short of the standard expected of a registered teacher.
She is accused of having sex with the boy in her car in a factory car park after picking him up after his lessons in 2008.
The hearing in Cardiff was told the English teacher, who worked at Rhymney Comprehensive School in Tredegar, South Wales, began a relationship with the boy – known in court as Pupil A - after one of his friends gave him her mobile phone number.
The panel was told that the boy's friend initially phoned the teacher from Pupil A's phone as a joke, and she rang back.
In his evidence, Pupil A, now 22, said: "We chatted and she put a bet on me not being able to keep up with her during sex."
He told the hearing that he had alerted Miss Ager to the fact he was a 16-year-old pupil at her comprehensive school, and she allegedly told him that everything would 'be OK' as long as he 'kept quiet'.
He said they then began to meet up daily or every other day for an hour or two after school, and would drive off to have sex in her car.
"We only ever had sex in her car," he said. "She said if people did find out I would be a legend. It continued for two months."
He said that his friends knew what was going on, and that Ager would also pick them up to go to McDonalds, and even let them drive her car.
Pupil A added that one of his friends phoned Ager to ask for a threesome, but she declined.
The former pupil told the hearing that the teacher bombarded him with phone calls and sexual text messages during their two-month affair, and claimed that she kept a photograph of his penis on her phone.
"On a school trip to London somebody saw she had a photo of my penis on her mobile phone but she said it was somebody else's," he alleged.
Pupil A ended the relationship to get back together with an ex-girlfriend.
The Mail reports that solicitor Martin Jones for the General Teaching Council for Wales told the hearing that Miss Ager was pulled into a meeting with her head teacher over the liaisons. As a result of that meeting, she offered her registration, which was accepted, and she left the school.
Miss Ager did not attend the disciplinary hearing and has failed to answer the charges put to her.
The hearing continues.