A teaching union has demanded compulsory parenting classes for everyone to combat rising levels of illdiscipline in schools.

The call came in the wake of findings by education watchdog Ofsted that showed drug taking, weapons, and gang culture were rife among pupils.

Based on visits to 78 schools in eight local education authorities, including Sandwell and Shropshire, the report found bad behaviour to be a problem in as many as half of all schools.

A fifth of secondaries perceived gang culture to be widespread, while 40 per cent said pupils brought weapons into the playground or classroom at least once a term.

David Bell, chief inspector of schools used the report, entitled Managing Challenging Behaviour, to highlight the need for more effective leadership and training of teachers in controlling unruly pupils.

But the Birmingham branch of the National Union of Teachers claimed the emphasis on eradicating illdiscipline should be on parents, not teachers.

Nigel Baker, deputy general secretary of the Birmingham NUT branch, said: "The single biggest factor in children ' s behaviour and self-esteem is parents. We need to provide really good parenting classes. At secondary school, we should start talking about what it means to be a parent."

Mr Baker said the break-up of the traditional family unit meant compulsory parenting classes were needed to fill a knowledge gap. Where else are young people supposed to know about the most important job they will ever do?" he said.

"With the breakdown of the family, so many young people through no fault of their own are being brought up by people who don't know what do do. I am a parent myself - I know I could have done with parenting advice. You are just left to it."

He added: "We expect so much from teachers, but there are things that are determined before a child is at school."

Mr Baker called for parenting skills to be available to all parents, but with the emphasis on those with children aged up to five.

"If you want to change things, rather than putting sticking plaster on, we need to change things before they get to school," he added.

The Ofsted study, which was carried out by the University of Birmingham, found that when Labour came to power in 1997, 76 per cent of schools said they had good levels of discipline. That figure had fallen to 68 per cent by last year.

The proportion reporting unsatisfactory behaviour remained constant at just under one in ten. The report claimed drug abuse was "a daily challenge" for some older teenagers. But it stressed there was a lack of evidence to back up the perception of a widespread gang culture.

A spokesman for Department for Education and Skills said: "We fully back heads in taking robust action against any violent behaviour, including permanent exclusion.

"Most pupils don't carry knives - in or out of the classroom.

" There are 6.7 million pupils in England's 24,000 schools. There were 57 convictions last year for possession of a knife on school premises."

Earlier this year, Education Secretary Ruth Kelly promised a " zero tolerance approach" to ill-discipline in schools.

It includes a new drive to encourage local authorities to use parenting orders to reinforce parents' responsibility for their child's behaviour.