In the Fifties it was the teddy boys. In the Sixties it was mods and rockers. Then there were skinheads and now there are “gangs”. For decades, schools have had to cope with societies in which kids group together and pick on others for tribal reasons. But in a world where young teens in the know can pick up guns and body armour easily and use primary-aged children to “mind” their arsenals, schools can be in the firing line as gang rivalries threaten to spill out of the streets and through the school gates.

So how are successful schools working in the kind of areas where children get shot in their beds, at ice rinks or when they are cycling home from a party? And what can other schools, dealing with gang-style behaviour that doesn’t involve guns and knives but fists and bullying, learn from the practical successes of schools embedded in areas where the streets teem with armed teenage gangs?

To begin with, they do their best not to let the gang culture in. They know what is going on outside in the streets, they know the rival gangs and, crucially, they know their pupils and act quickly on information they feel risks the safety of their school communities.

A simple and recent example explains a lot. It was 2.30pm at a north London comprehensive last Thursday when the deputy head spotted a Year 10 Afghan boy sneaking off the site. He knew there was corridor gossip about a feud between the boy and another pupil, members of rival gangs, so his instinct told him to follow. It proved a wise decision.

Half an hour later, the teacher was telephoning the police, reporting the arrival of a gang of a dozen Afghan boys outside school, intent on coming on to the site to attack the boy from the “enemy” gang. The police arrived quickly, arrested a couple of the gang at the gate and dispersed the rest.

The school day ended peacefully.

“It’s a huge part of our job, protecting pupils while they’re here from the evil influences outside,” says the teacher. “We’re increasingly aware of the potential for post-code turf wars breaking out in school, and we know the pupils likely to be involved. I’ve learnt to recognise gang members’

tags (graffiti-style signatures) written on their exercise books.”

Community intelligence and vigilance by teachers is essential. The murder of 15-year-old Billy Cox in his south London home has cast a frightening shadow across several local schools. “A lot of the kids were really upset and couldn’t stay in lessons because they were crying,” says Alice Diamond, a Year 10 tutor at Chestnut Grove School, Balham, where some of Billy’s former friends go.

Billy attended Ernest Bevin College in Tooting until behaviour problems forced him to leave a few weeks before his death. After that he put in a handful of appearances at a pupil referral unit in Kennington. The scores of messages from Billy’s friends left on a website set up in his memory - with references to him as a “fallen soldier” and to the way gangs and guns have become endemic locally -opens a depressing window on to the world inhabited by secondary age pupils in this area.

And the list of schools around the country bearing similar scars has grown dramatically in the past year. Billy’s was the third teenage killing within a week in south London, all involving guns. Some of the children involved have no connection with gangs but are just in the wrong place at the wrong time.

Last summer Kiyan Price, 15, was fatally stabbed as he came out of the London Academy in Edgware, only a week before a 14-year-old boy survived a similar knife attack outside a Birmingham school. In September, Jessie James, also 15, from Manchester Academy was shot dead in the Moss Side area of the city as he cycled home from a party. His fellow pupils dealt with the tragedy in part by selling lapel badges to raise money for a bench in his memory.

Although incidents resulting in death are relatively rare, cases of lower level gang violence linked to schools are more common. At the end of last year, police in west London had to break up a pitched battle between rival gangs, some armed with chair legs, from two west London schools. Last week teachers at a school in the same area called in the police when graffiti alluding to violent gang rivalries appeared on a wall on the school walks.

But the fact that teachers crack down on gang behaviour and there has not been serious gang violence at school shows how effective they can be at containing the situation - at least while the pupils are at school.

“When we see our kids away from school, they’re all in gangs,” says Neville Beischer, headteacher of Wright Robinson Sports College, a large comprehensive serving some of the most deprived parts of east Manchester.

“We know there are guns, knives and drugs out there, but they don’t bring them in here, because we’ve created a different culture.”

Neville imposes strict rules on school uniform. He’s on the gates every morning, checking that nobody comes in with hoodies, hats, baggy trousers, or “bling” jewellery. “We effectively disarm them of anything that goes with their street culture, forcing them to look, and consequently behave, more like children.”

The school also reversed a trend of violence on school buses by putting a teacher or learning mentor on several buses every morning and evening. “Our buses used to come to school half empty and parents told us the kids were too scared to use them because of gangs. Now they are all full.” Similarly, playgrounds always have three staff on patrol. “I can’t remember when we last had a fight,” says Neville. “And by cutting out fights, you cut out gangs.”

At Kingsmead School in Enfield, north London, an area reputedly blighted by 12 local gangs, a similarly safe climate has been established, using different methods. A CCTV system constantly watches corridors, toilets and potential trouble spots inside school and around the perimeter, and there’s a small dedicated team of staff, including one ex-policeman, who react instantly to any instances of aggressive behaviour.

“There’s a frightening gang culture outside, which our young people risk being drawn into,” says Giles Bird, headteacher. “We try to provide something that’s different and keep anything else well away.”

A strict rule he imposes is that, after school, he allows only family members to meet pupils at the gates. If they are seen with anyone else, they’re brought back into school.

Like many schools, Kingsmead now has a secure perimeter fence and its own full-time police officer, Don McMillan, who thinks about 5 per cent of the school population exists in or on the fringes of the gang culture. But as well as embodying the preventative role of the police, he also tries to have a remedial effect on pupils. “I know the ones in danger of becoming robbers,” he says, “And I try to work with them in school, and encourage them to get involved in positive activities to keep them away from crime.”

And away from the worst inner city areas, there are plenty of schools countering any aggressive or violent culture outside. At Pool Community College in Cambourne, Cornwall, Jeremy Rowe, deputy headteacher, champions the influence a school can have as a force for good. “To keep negative values out of school you have to take your own positive values into the community,” he says.

So, as well as visiting the parents of problem pupils in their homes, the school involves itself in the running of a local youth club, and organises events such as skate boarding trips for local teenagers. “Schools can really become beacons of hope,” he says NO HIDING PLACE

A teacher’s guide to keep gangs outside school

* know what is going on outside in the streets - know the rival gangs

* know your pupils

* act quickly on information

* strict school uniform. No “street” clothes - hoodies, hats, baggy trousers, or “bling” type jewellery

* have teachers or other adults supervising on school buses

*put sufficient staff on playground duty to deter fights

* install CCTV in corridors, toilets and potential trouble spots inside school

* have staff patrol the site perimeter

* strengthen links with local police and find out if an officer can be based at the school

* allow only family members to meet pupils at the gates after school

* visit the parents of problem pupils at home

* run a youth club

* organise events such as skateboarding trips for local teenagers.