It is not the first time the Pakistani Taliban have shot up a school. Their war on education has been a long and deadly campaign that has seen more than a 1000 schools bombed or burned.
But Tuesday's attack on the Army Public School and Degree College in the north-western capital of Peshawar was the bloodiest.
The immediate justification for this appalling attack is the Pakistani military's offensive against the Taliban leadership, which is based in North Waziristan.
Yet that offensive was triggered by the Taliban's most audacious attack on the Pakistani state itself in June, when 10 Taliban militants laid siege to the international airport in Karachi - Pakistan's biggest city - and waged an eight-hour battle with security forces that killed 10 people.
That attack left the already fragile government of newly elected Prime Minister Nawaz Sharif - himself a hugely controversial veteran of Pakistani politics - no choice but to launch an all-out attempt to bring the Taliban under control.
Perhaps the real motive for Tuesday's massacre was the sight on Monday of Pakistani schoolgirl Malala Yousafzai being awarded the Nobel peace prize in Oslo.
It was her campaign for female education that so enraged the Pakistani Taliban that in October 2012, a Taliban gunman shot her in the head as she was riding a bus home after taking a school exam. Miraculously, she survived.
Speaking from London, Malala condemned Tuesday's attacks.
"I am heartbroken by this senseless and cold-blooded act of terror in Peshawar that is unfolding before us. Innocent children in their school have no place in horror such as this," she said.
"I condemn these atrocious and cowardly acts and stand united with the government and armed forces of Pakistan whose efforts so far to address this horrific event are commendable. I, along with millions of others around the world, mourn these children, my brothers and sisters - but we will never be defeated."
What the attack clearly demonstrates is the conflict at the heart of the Pakistani military and political establishment, half of which not only sympathises with the Taliban's aims, but actively supports its activities, while the other half recognises the threat the Taliban poses to civil society.
Somehow, Sharif must unite the military and security services and finally defeat the Taliban.
Lurking in the background all the while is the dangerous demagogue and former international playboy Imran Khan, whose national campaign of public protests claiming that Sharif came to power by fraudulent means have severely undermined the prime minister's authority.
Khan has already cancelled further nationwide protests in the wake of the latest attack. He would do well to put his vanity aside and stop calling for more useless negotiations with the Taliban until he has something constructive to say.
