By Hannah Goff
BBC News at the NUT conference, Manchester
Schools can use detectors to screen for weapons
A growing number of pupils are taking offensive weapons and drugs into a hard core of schools in troubled areas, research suggests.
The proportion of teachers finding weapons on pupils on a weekly basis had almost quadrupled from 2001 to 2008.
Warwick University, interviewing 1,500 teachers for the National Union of Teachers, found those finding drugs on pupils weekly had doubled.
The government said the majority of schools were safe places.
Overall, the share of teachers who had never found drugs or weapons on pupils has grown.
But one in four said they had found an offensive weapon and one in five said they had found pupils possessing drugs.
A staggering one in 10 teachers had discovered children dealing in drugs.
Highlighting the research at his union's annual conference, the NUT general secretary Steve Sinnott said the picture that was emerging was one of polarisation taking place within schools.
"Overall there seems to be an improvement, but this core group of schools are still reporting this very significant issue."
Mr Sinnott said: "We know what has occurred in particular areas - we know what has occurred in south London and some areas of Liverpool.
"In one particular area of Manchester - Mosside - the life expectancy of youngsters is below the age of 30."
But head of education John Bangs cautioned against assuming the schools in question were in deprived inner city areas.
He said there were troubled schools in rural areas and on edges of large towns as well.
Mr Sinnott said teachers needed extra support to deal with violence and drugs and urged the government to help by tackling poverty.
It was only by tackling both adult and child poverty and social disadvantage that such problems could be addressed in the long-term, he suggested.
He added that schools should be drugs and weapons-free and their discovery on pupils should lead to permanent exclusion.
The Department for Children, Families and Schools said the majority of schools are safe places to learn and work and the use of weapons is extremely rare.
A spokeswoman said: "Schools are able to screen pupils for weapons using "arch" and "wand" metal detectors to ensure that such weapons are not taken onto a school site.
"We have also given heads and school staff tough powers to conduct hands on searches of pupils."
She added that the government backed heads taking tough decisions over exclusions.