And the government must better resource its policy of inclusion of special needs children in mainstream classes to ensure other pupils' education does not suffer, according to the Ulster Teachers' Union.

"As the number of pupils with behavioural needs in the mainstream rises, teachers must be adequately trained in how to protect themselves and other pupils," Avril Hall Callaghan, general secretary of the Ulster Teachers' Union, told UTU delegates at their annual conference today in Newcastle, Co Down.

"We are also treading a fine line because children and their parents are so litigious.

"A teacher involved in breaking up a fight between pupils could just as easily be injured themselves or be accused of assaulting the young people.

"The appalling case recently of a teacher whose trousers were pulled down in front of a class just highlights the sort of behaviour that teachers may have to face."

A mobile phone was used to film this incident at a Belfast school and it was put on the internet within minutes.

Fred Brown, incoming president of the NASUWT teachers' union, has already claimed it would not be long before a teacher was "raped, filmed and on the internet", and he called for all mobile phones to be banned from schools across Northern Ireland.

Earlier this month, the Irish National Teachers' Organisation also warned that pupils as young as four-years-old are attacking other children.

Qualified teacher Diane Nugent, who works in Belfast's Park School and Educational Resource Centre for children with moderate learning difficulties, backed Ms Hall Callaghan.

She said: "All students who attend the secondary school have statements of special education need.

"They have a range of needs such as ADHD, Autism, Asperger's, Down's syndrome etc, but a growing number are there simply due to low numeracy and literacy levels.

"Due to past negative school experiences, behaviours emulated in the classroom are the result of the frustration that is deep-rooted in these children.

"I was in my second year of teaching before I received training in positive handling strategies to manage the kind of behaviour which is becoming more prevalent in the classroom context.

"A teacher in another special educational unit received training in her first week and was told she'd have to use the techniques maybe once a year.

"In fact, she needed them the next day when a fight broke out between pupils and a male teacher was injured as he tried to separate the boys involved.

"It's a very daunting situation for a young teacher, often a young woman, to face when they're trying to split up two brawling 16-year-olds."