Women mourn their relative Mohammed Ali Khan, 15, a student who was killed during an attack by Taliban gunmen on the Army Public School, in Peshawar on December 16, 2014.

The attack on a school in Peshwar in northwestern Pakistan that left at least 145 dead – almost all of them children – sets a new low of depravity for the Pakistani Taliban. Tragically, the attack, while horrific in scale, is but one of an all-too-frequent pattern of deliberate attacks on schools both in Pakistan and worldwide.

The Pakistani Taliban splinter group, Tehreek-e-Taliban (TTP), justified the attack against the military-run school – where militants systematically went from classroom to classroom shooting children and teachers – as revenge for an ongoing army offensive in the tribal areas of North Waziristan that began in June. Taliban spokesman Muhammad Umar Khorasani said the attack was intended to make the army “feel the pain” for allegedly “targeting our families and females.”

Today’s attack is of incomprehensible horror and brutality, even for a group that has already shown well-documented contempt for the lives of civilians. In its war against the Pakistani government, the TTP has frequently violated international humanitarian law, which forbids armed forces of any kind from subjecting civilians to deliberate, indiscriminate, or disproportionate attacks. It was the TTP that shot Malala Yosafzai in the head in 2012 for fighting for girls’ education.

Between 2009 and 2012, there were at least 838 attacks on schools in Pakistan, leaving hundreds of schools destroyed. Worldwide, some 30 countries have experienced a pattern of intentional attacks on schools, teachers, and students in the last five years, according to the Global Coalition to Protect Education from Attack, a group of nongovernmental organizations and three United Nations agencies that work together to prevent and respond to such attacks. The Coalition has documented the killings of hundreds of students and educators, with many more injured, during that time. That violence has also denied education to hundreds of thousands of people or forced them to study and teach in fear.

At the very time of the Peshawar attack, 37 countries, led by Norway and Argentina, together with 10 international organizations, were meeting in Geneva to promote the need to protect education in wartime. This tragically timely event launched the Guidelines for Protecting Schools and Universities from Military Use during Armed Conflict.

As Peshawar reels from today’s attack, many Pakistanis will look to the government of Pakistan to improve security at its schools to protect students and educators from future such atrocities. The government should also strengthen its efforts to arrest and prosecute TTP militants and others who target schools for violence. Other countries can demonstrate solidarity with the victims of the Peshawar school attack by not only expressing outrage, but by endorsing the Guidelines as an expression of determination that such attacks must come to an end.