Cut-out cardboard hearts, stars and a slogan that cheerfully declares “The Earth Laughs In Flowers” adorn the classrooms of the Ummat Public School in the Pakistani city of Quetta.

The bright images cannot dispel the sense of foreboding shared by dozens of teenage girls seated at their desks, all members of the town’s Hazara community.

Soon they will finish their exams and expect to go to college. Only these young women will stay at home. A killer is on the loose in Quetta, and their parents are terrified.

Amina, 15, raises a hand.

“I wanted to go to the best college; my dad says ‘It’s not important.’ In our family everybody is frightened,” she said, as pupils in white headscarfs nodded glum-faced assent.

“I don’t want to live that life where I can’t get education,” she said. “I don’t want to be an ignorant person.”

In Pakistan, it’s not unusual to meet people who have suffered unfathomable grief at the hands of men who have arrogated the right to take another’s life in the name of religion.

But there is something uniquely dispiriting about seeing the ambitions of articulate young women being snuffed out by a systematic and preventable campaign of targeted killing.

The capacity of Pakistan’s militants to persuade themselves of their own moral authority was made clear this month when the Taliban issued a lengthy justification for its decision to shoot Malala Yousufzai, a 14-year-old schoolgirl who had championed female education.

The killer at large in Quetta is Lashkar-e-Jhangvi, a Sunni extremist group whose adherents see members of Pakistan’s Shi’ite minority as infidels deserving of capital punishment.

Hazaras make particularly attractive targets. Not only are they Shi’ites, but they are also descendants of émigrés who escaped a previous wave of persecution in Afghanistan in the 19th century. Such “otherness” was not an issue in Pakistan in the past. Now, it is a death mark.

Attacks on Hazaras have been escalating since 1999, but this year the militants have beaten their previous personal bests, killing more than 100 in the first eight months of the year alone.

The grip LeJ exerts on Quetta is difficult to appreciate from the drawing rooms of Islamabad, where brief reports of bombings or assassinations carried on the inside pages of newspapers fail to capture the scale of the persecution now faced by the city’s 500,000 Hazaras.

In the winding lanes of Mehrabad, a Hazara enclave on Quetta’s eastern edge, the impact of the LeJ’s handiwork is easier to grasp. It would be wrong to describe the district as a “ghetto” — the word conjures images of deprivation and squalor that are at odds with the meticulously swept streets.

On a recent morning, gaggles of schoolchildren in waistcoats and ties scurried past traders pushing handcarts laden with melons, while women snatched scarves across their faces when they spotted a visitor raising a camera. The neighbourhood felt like a place where people are proud to belong.

Not a “ghetto” then, but under the veneer of normality, Mehrabad is slowly becoming a jail.

Hazaras risk being shot every time they venture beyond the district. The day a Reuters reporter arrived, gunmen opened fire on a taxi, killing three people instantly and critically wounding two others. Such attacks are now routine.

Fearing attack, Hazara traders have closed shops in bazaars in parts of Quetta where in the past they had mingled easily with Baluch, Pashtuns, Punjabis, Sindhis and Hindus. A once-cosmopolitan city is turning in on itself, riven with invisible divides.

Pakistan’s tragedy is that Quetta is by no means an anomaly. The city’s quiet fragmentation is a microcosm of the way in which Pakistan’s leaders have allowed a fanatical fringe to poison the country’s deep wells of tolerance with a toxic vial of prejudice, chauvinism and fear.

Pakistan’s generals and politicians are rightfully eager to remind the world that they have sacrificed many more men fighting the Taliban in the rugged north-west of the country than NATO has lost in Afghanistan. But in Quetta, the excuses for failing to stop the killings ring hollow.

The onslaught against the Hazaras could easily be blunted — if the will existed to do so. This is not an isolated village in the Hindu Kush, nor is it an intimidating metropolis on the scale of Karachi, the mega-city of 18 million people where LeJ has also been hard at work. With a population of about two million, Quetta, the capital of the vast province of Baluchistan, has a small-town feel. It must once have been rather pleasant.

It is easy to predict where the attacks will take place. Many occur on Spini Road, which links Mehrabad to Hazara Town, the other main Hazara enclave which lies on the other side of Quetta. The assassins roar up on motorbikes, open fire, and are gone. They are never caught. It is a measure of their confidence that they do not bother to wear masks.

Hazaras interpret the state’s failure to halt LeJ’s campaign as a sign that elements within the security forces are turning a blind eye, if not actively abetting the killers. It is no secret that LeJ was sponsored by Pakistan’s intelligence agencies as a proxy to fight in Kashmir in the 1990s. The group has since been banned, but nobody is quite sure how far its old connections have endured.

Hazara suspicions intensified in 2008, when two LeJ commanders performed a Houdini-like escape from a high-security jail in Quetta, according to Khaliq Hazara, chairman of the Hazara Democratic Party. He says many attacks take place within sight of checkpoints manned by security forces.

A short drive from Mehrabad, sentries in sand-bagged machine-gun nests guard the headquarters of the Frontier Corps in Baluchistan, a paramilitary force that traces its heritage to the days of the British Raj, when camel-mounted troops traversed the region’s forbidding deserts and wadis. Something of that bygone era persists in the officers’ penchant for berets and swagger sticks.

A formidable figure in freshly-pressed fatigues, Major-General Obaidullah Khan, the commander of the FC in Baluchistan, says his force’s efforts to catch LeJ suspects are hindered by their group’s ability to infiltrate Quetta from others parts of Pakistan.

“They come from outside, remain for a short time, operate and just vanish. Whenever we have got a chance we have operated against them,” Khan said. “We will not spare them. For us there is no exception.”

Hazaras say they have not heard of a single case of an LeJ suspect being prosecuted.

In private, some members of the security forces are less than sympathetic to the Hazaras’ plight. One officer argued – in apparent seriousness – that wealthy members of the Hazara community were orchestrating the attacks on their poorer brethren to win sympathy from Western governments to make it easier to obtain visas.

Quetta’s political elite have also shown scant solidarity. When asked about the violence, Aslam Raisani, Baluchistan’s chief minister, once told reporters he would send a “truckload of tissue paper” to mourning Hazaras so they could wipe away their tears. Hazaras were incensed at the remark.

It is no surprise then that thousands of Hazaras are turning to people smugglers to spirit them to Indonesia, where they board decrepit, overloaded fishing boats in the desperate hope of joining thriving pockets of Hazara immigrants in Australia. Many have drowned.

No tour of Mehrabad is complete without a visit to the Hazara cemetery, a bleakly peaceful spot overshadowed by a bald hillside. Founded in 1896, the graveyard has had to expand rapidly in recent years to accommodate LeJ’s victims, whose faces stare from portraits placed on their headstones. Mourners leave clay dishes of water on the tombs, believing birds will say a prayer for the departed each time they swoop down to drink.

Every day, Azroa Safdder uses a plastic bottle of water to wash the dust from the marble marking her son’s resting place. An assistant to a high court judge, her son was shot by militants in Quetta last year, shortly before he was due to be married.

“I devoted my life to my child, but the terrorists killed my son. Now without my son I don’t want to live any more,” Safdder said, hunched over the grave. She wrapped her shawl around her face to hide her tears. “The light of our home is out.”