More police officers and better family support are needed to tackle increasingly violent schoolchildren, a Bradford teachers' leader and councillors claimed today.

Their call follow a report today which claimed almost half the nation's youngsters, aged 11 to 17, have committed a crime.

The survey, conducted among 14,000 youngsters by the Joseph Rowntree Foundation, also revealed the extent of alcohol abuse among youngsters, with four out of ten students in Year Ten revealing they had "binged" on drink.

Violence, including weapon-carrying and fights, are an "acknowledged part of life" for a significant number of young people, especially boys.

And researchers found one in ten boys aged 11 to 12 admitted carrying a knife or other weapon in the previous year, rising to one in four by Year 11.

Today a teachers' leader in Bradford said the increasingly bad behaviour was making teaching impossible and was the single biggest reason why there was a shortage of teachers.

John Haworth, treasurer of the Bradford branch of the National Union of Teachers, said teachers needed Government help to clamp down on unruly pupils who were disrupting other pupils' education.

"All too often youngsters who have been excluded from other schools are just dumped somewhere else. We need proper support for the school and the help of parents in tackling anti-social behaviour."

Councillor Andrew Carter (Con, Pudsey) complained of police inaction in relation to the growing yob culture and said firm action was needed. "With the increasing levels of crime and anti-social behaviour being committed by gangs of youths roaming the streets and causing huge distress and nuisance to local people, it is clear that something needs to be done. We cannot allow our streets to become crime-ridden.

"The Government must start to pay for more police. Visible policing combined with tough penalties are, in the end, the only way we can crack down hard on youth crime and anti-social behaviour."

And Coun Clive Richardson, of West Yorkshire Police Authority, said the report reiterated the need for more police officers. "Poor parental supervision and broken homes are cited as a major factor in youth crime. We must work with youngsters and families to stop them getting to the stage where they are out of control."