“Whoever stole the most, or had the biggest knife, was the biggest man there. And you wanted to be that guy,” he says. “We thought it was cool to steal – we really weren’t making the right choices.”

Choices are the theme of the day for this class of nine- and 10-year-olds. Carpio, social outreach co-ordinator of the church next to the school, has been invited in to lead a drama workshop about good and bad decisions. The class have been acting out little scenarios: pick up that purse and take the money, or take it to the police? Bully the new kid at school, or make him a friend? But they know there’s a darker theme underpinning the exercise. Carpio’s visit is part of a class project on knife crime, and the aim is to make them think about decisions they may one day have to make about whether to carry a weapon.

St Ignatius is among a growing number of primary schools that have decided to tackle the issue head-on – often prompted by their pupils. According to the Citizenship Foundation, under whose auspices this class are running their project, knife crime is one of the top three issues named by this age group as their most pressing concerns, along with the environment and health. And although the charity hasn’t yet assessed what proportion of schools taking up its “Make a Difference Challenge” – under which children choose a topic to tackle in their local communities – are looking at knives or other violent crime, it says a very significant proportion have done so.

It is certainly a topic in which this class is interested, not to say fascinated. They start off shy – “Why am I looking at three hands when I have 24 children in front of me?” exclaims the class teacher, Justa Fernandez. But within minutes there’s a sea of waving hands and voices crying: “Miss! Miss!” Everyone has an opinion. Some have suggestions about how to avoid getting involved: “Sometimes you just have to say ‘no’ to people,” Naysha, 10, suggests. Some want to share their experiences: Evita, 10, tells a story about how her brother was mugged three times for his mobile phone. “It was because he lived in N16,” she says. And some, particularly a few of the boys, just really want to share their knowledge on the subject. “People just want you in their gangs, so they don’t get in trouble – they stab people and run away,” says Jezreel, nine.

And that’s hardly surprising: these children could hardly be unaware of the effect of knife crime in their local community. On the front of the church next door to the school hangs a huge banner, which reads: “Isaiah 2:4: They will hammer their swords into ploughshares”. Underneath it is a knife amnesty bin into which people can place their weapons, dedicated to the memory of two young local men stabbed to death recently in separate incidents. One of them, a talented 17-year-old footballer named Godwin Lawson, who was killed last year, was a former pupil at St Ignatius, and some of Fernandez’s class knew his siblings.

Nationally, knife crime is on the wane – there were 210 murders involving knives or other sharp instruments in 2009-10, compared with 270 two years earlier. Yet there’s no denying it’s a real issue for the children at St Ignatius. The children chose the project themselves after drawing up a list of things they’d like to change about their area. The final choice came down to a vote between knife crime and pollution – and crime won hands down.

Over the last three months, they’ve been building the subject into their normal lessons. Work on persuasive writing produced a list of slogans, now pasted boldly on to the white board: “If you use a knife, you could delete a life”, “Drop that knife – don’t waste my time”. A surgeon has been in to talk about her experiences of treating knife-crime victims, and the local police have also been invited.

The subject has clearly caught the children’s imagination. Yet there’s no suggestion any of these pupils have been tempted to get involved in gangs or knife crime themselves. So why are they so seized by the issue?

Fernandez says it’s often on their minds: “It’s all around them; it’s on the news. They’ll often come in on a morning and say, ‘Did you see the news last night?'” she says. “Godwin Lawson went to school with one of our girls’ older brothers. She said in class that it made her sad when she heard his name mentioned.”

But while St Ignatius is in a high-crime, inner-city area, pupils from other districts are concerned, too. Marguerite Heath, director of Go Givers, the Citizenship Foundation’s main programme for primary schools, says it’s important to address their fears head-on.

“I think a lot of children do get quite concerned about this type of thing, particularly when they start to move on to secondary school,” she says. “When they start to travel around on their own, rather than going by car. And I think on the whole we try to protect them too much, actually. A lot of this is to do with peer pressure – children get pressured into belonging to gangs, and this kind of programme gives them opportunities to rehearse the skills and practice the values they need to overcome that.”

Leading campaigners on knife crime have argued that all children should learn how to make themselves safe – and should do so as early as possible. Earlier this year, Brooke Kinsella, the former EastEnders actress whose brother, Ben, was stabbed to death during a night out in north London in 2008, produced a report on the subject commissioned by the Home Office. It argued that all pupils should learn about knife crime during the last years of primary school, as the St Ignatius pupils have done this year.

But some sceptics say these efforts could prove counterproductive. Dennis Hayes, head of the Research Centre for Education and Career Development at the University of Derby, argues that there is a lack of solid evidence showing the effectiveness of such programmes.

“I think that unless they are thought through, initiatives with the best intentions can do a lot of damage,” he says. “For most kids, knife crime isn’t really an issue. Making them think about it is a bit like making people think about suicide. The message they get is that knife crime is a real problem, so perhaps they should carry a knife.”

Heath does not agree: “I think if you don’t address these issues that the children are thinking about, then misunderstanding grows and they can’t get on top of it,” she says. “The idea of the ‘Make a Difference Challenge’ is that they are finding a way they can actually do something about it, so they feel empowered, and once you feel on top of something, it’s no longer frightening.”

Some of the class have brought their own personal experiences in to share during the last two months. During our discussion, Olivia, 10, has been sitting with her hand up, but perhaps too shy to push herself forward. Eventually, Fernandez invites her to speak. “Not long ago,” she says, “someone stabbed someone near my house. And that made me think about knife crime. I felt that person’s family must be really sad about what happened.”

The bilingual support assistant, Maria Miele, prompts her: “Tell me what you told me when you came in that morning.”

“I thought maybe I would see them,” she says. “And maybe they could do something to someone I knew.”

The headteacher, Con Bonner, says it’s hardly surprising the children are frightened by such incidents when they happen so close to home: “It’s the environment where they’re living,” he says.

“It’s a topic that’s discussed among young people generally. Literally in the streets they walk up and down, these events take place.”