A senior teacher whose girlfriend was the object of sexual gestures from a special-needs pupil attacked and injured the teenager, a disciplinary panel has heard.
David Thomas, known to colleagues as Kevin, was seen lying on top of the 15-year-old boy at Ysgol Bryn Castell special school in Bridgend after shouting at him in a side room.
The boy, referred to as pupil A, was left with facial injuries and marks to his body after the incident, which took place in November 2006, a disciplinary hearing at the General Teaching Council for Wales (GTCW) was told.
Mr Thomas, who taught craft, design and technology at the school for 18 years, was suspended and then dismissed following an internal investigation, but was later cleared of assault charges at Bridgend Magistrates Court.
However, he could be banned from returning to the classroom if found guilty of unacceptable professional conduct by a GTCW committee.
Mr Thomas is accused of reprimanding pupil A when it was not his responsibility to do so, and acting outside the school's behaviour policy. He denies both charges.
Presenting officer Gwenno Hughes told the hearing that a female member of staff, referred to as teacher C, alleged that pupil A had made obscene gestures towards her.
Mr Thomas, who was in a relationship with teacher C, sought out pupil A and found him in a quiet room where pupils with behavioural difficulties are taken to calm down.
Witnesses Gareth Lewis and Lee Tucker both saw Mr Thomas talking with pupil A in the quiet room, but left as they thought the matter was under control.
They returned to the room after hearing Mr Thomas raise his voice, followed by the sound of moving furniture.
Mr Lewis, head of PE at the school, said: "I saw pupil A lying on the floor on his back with Mr Thomas lying on top of him." Mr Lewis told the GTCW that Mr Thomas said: "Don't you dare ever raise your fists to me again."
Behaviour support manager Mr Tucker said pupil A was "tearful and shook up", and told them: "I'm not happy, he can't do that to me."
A check on pupil A recorded a swollen eye and top lip, marks on his back, neck and chest and finger marks on his arms.
Mr Lewis admitted that the school's behaviour policy at the time was "confusing", but said staff would automatically turn to Mr Thomas, who had a responsibility for discipline.
Mr Tucker also understood that this was part of Mr Thomas' role.
Mr Thomas has yet to give evidence, but in a police interview read out at the hearing he said he wanted to speak to pupil A because he abused a female member of staff, not because she was his partner.
He claimed he grabbed pupil A's wrists because he thought he was going to be attacked.
"Pupil A went to stand up with his fists raised, I took hold of both his forearms but my leg buckled and we fell to the floor," he said.
Detective Constable Paul Hatton, who conducted the interview, said Mr Thomas admitted leaving marks on pupil A's arms where he had grabbed him, but could not account for the facial injuries.
The boy claimed Mr Thomas kicked his legs from under him and threw him on the floor.
But Mr Thomas said: "There's no way the incident went the way pupil A stated. They are children, we are adults. I wouldn't do that to a child."
Andrew Williams, a child care officer at the school, said Mr Thomas was a very good teacher who would "not lay a hand on a pupil".
He said pupil A was one of the worst-behaved pupils he had seen at Bryn Castell, and that he could "go off like a bomb for no reason at all".
The hearing will resume in March.
Code calling: governor and parent views invited
The GTC wants the views of parents and governors on its controversial proposed code of conduct for teachers before the consultation period ends this month.
The code seeks to set out minimum standards and to give clarity to expectations of teachers by the profession and society as a whole.
But when the proposals were outlined last October, teaching unions dubbed them "flawed", "disturbing" and "demeaning".
Although the GTCW maintains the code is an evolution of existing guidelines, several unions said it was too prescriptive and offered no help or support to teachers.
Experienced and newly qualified teachers gave their views on the proposals at special focus group sessions in mid and north Wales yesterday.
Heads and deputies will have their say at a session in south Wales on Monday.
The public consultation ends on January 31. www.gtcw.org.uk.