Today, and for many mornings to come, Linda Walker will be waking up in Styal prison, in Cheshire. There are better places to spend a Sunday. Six women killed themselves there in the space of a year and 41 tried to hang themselves over the last Mother's Day weekend. Mrs Walker, 48, is a teacher and head of year at a school for children with behavioural problems. She has a partner who is a college lecturer, twin sons of 17, a daughter and an elderly father for whom she cooks. Last week, she was jailed for six months after carrying out the sort of fantasy to which some liberals furtively confess. She showed the yobs what fear feels like.  In Mrs Walker's account, her house had been under siege. Bicycles were stolen, fish disappeared from the garden pond and wing mirrors were smashed. An abusive caller said her son was a 'poof' and asked: 'Does he want a good bumming?' On 14 August last year, Mrs Walker snapped when a container of liquid was poured over a family car  After haranguing a group of teenagers, she returned home to arm herself with a Walther CP88 gas-powered air pistol, which she had kept in her underwear drawer since a previous burglary, and an air rifle. Pausing only to phone the police to tell them that she was 'going to shoot the f****** vandals', she fired six times at the ground near an 18-year-old youth.  Exit Mrs Walker, her career almost certainly in ruins, complaining that the law supported 'yobbos and not victims'. The court heard later that she had acted in a moment of madness to defend her family. Anyone could write the script from this point onwards. As mainly right-wing newspapers clamoured for her freedom, Michael Howard made her the official martyr of his campaign to 'put fear into the heart of yobs'.  So far, so predictable, except that the Walker case, far from confirming entrenched opinions, confounds many of them. For a start, conservatives are correct to challenge her sentence. Prison is for those whose crimes are so grave or who are such a danger to the public that no other option is possible. Mrs Walker fulfils neither criterion, and, like thousands of other British women, she should not be there.  Harsh sentencing does not, though, excuse her behaviour or explain it. I have just been burgled and my neighbour had her basement stripped bare three days ago. Neither of us felt impelled to add a Terminator-style armoury to our underwear drawers. In her defence, Mrs Walker was reacting against something more insidious. Kierkegaard called anxiety 'the dizziness of freedom', but nothing makes people feel more unfree than being constantly under threat. And so Mrs Walker, a respectable teacher, staged a conversion almost as startling as if Miss Jean Brodie had become a Clockwork Orange droog.  Greater Manchester, where Mrs Walker lives, does not resemble Kubrick's urban nightmare. Indeed, the showcase for the government's anti-yob strategy should be getting safer by the day. No other police force has been so eager to hand out antisocial behaviour orders, making the patch the Home Office's model of good practice. In a six-month period last year, 155 people were Asboed, compared with 27 in Merseyside.  Mrs Walker's story, and her son's claim that she had vainly asked the police 15 times for help,   offers only an isolated example that all is not well in Asboland. But then the government, despite the focus on expanding its crackdown, hasn't been very scientific either. We know that a third of orders are breached and that two-thirds of those sentenced for failing to comply are sent to jail. There are worrying reports of children who are mentally ill or frail being criminalised. But six years and 4,000 orders after the policy's inception, there is not a single longitudinal study to show whether the orders stop bad behaviour or, as many experts on youth crime believe, make it worse.  That question matters more than pre-election chatter allows. The jailing of Linda Walker may be unjust, but it is much less alarming, in the story of badland Britain, than the spate of child offenders currently appearing at the Old Bailey. Last month alone, three schoolboys stood trial for murder there. One in 10 12-year-old boys and a quarter of 16- years-old boys have gone out armed in the last year.  Fear is for bigots and for politicians more adept at conjuring despair than dreams. Michael Howard talks up terror. The Archbishop of Canterbury knocks it down. Liberals, appalled by being asked to beware the gypsy, the asylum seeker, the immigrant and the kid outside the chip shop, think dread a disreputable emotion. But suddenly I am afraid.  My fear began when Hakeem Johnson, aged 13, walked into my local takeaway and stabbed a young manager to death because he would not serve him a 1 pizza after a special offer had ended. I am not personally frightened of Johnson's friends, whom I probably brush past often in the Holloway Road, but I am scared by the statistic that three-quarters of boys excluded from school, as he was, have used a weapon. I am disturbed that a teaching union   has reported a surge in classroom violence, and the government must be anxious, too, because the Schools Minister last week announced a knife amnesty to tackle the 'hugely disturbing' culture of weapons.  But most of all, I am alarmed that, despite the overall fall in crime, a new mood of casual cruelty is fermenting in cities where the problems, and solutions, are mostly arcane and intractable. Atrocious families and deprivation are nothing novel and the government has done some good things to tackle both; 100,000 children lifted out of poverty last year is not enough, but it is slow progress.  So why the knives and the gangs of teenagers practising the elastic-hipped swagger of the pretend assassin? Why the wave of rapes and murders combining adult savagery and the capricious pointlessness of childish rage?  I do not know and nor does the government. But I think, and so do charities working in the field, that a society driving wedges between adult authority and alienated youngsters can only ignite the problem of children who evolve so fast from victims to aggressors.  That is not to suggest that the mean streets of Greater Manchester and elsewhere can be sanitised by a combination of table tennis and a willingness by law-abiding citizens to have their lives made miserable in the interest of community relations. But neither is it right to beat the drum of punishment and exclusion while saying so little about positive intervention.  Linda Walker's jailing was not only extreme. It also helped reinforce the narrative, only patchily accurate, about a middle class terrorised by yobs. Politicians like that story. It strikes a chord with anyone who has had their windows smashed or their geography class made hell. It offers slick solutions to the genuinely persecuted. And it stops anyone asking whether today's tearaways are being officially groomed for tomorrow's knife gangs.