Ban said the right to education for all must be firmly protected and reaffirmed that attacks against students, teachers or schools can never be justified.
Schools and educational facilities must be respected as safe and secure spaces, he said.
The UN chief is appalled by such acts of violence and calls for the perpetrators to be swiftly brought to justice, his spokesman said in a statement.
The Secretary-General recalled, just over a year ago, Pakistan experienced one of the deadliest school attacks in its history near the city of Peshawar, where more than 150 people died, mostly children.
Calling for proportionate and necessary measures to be taken to ensure that schools in areas of insecurity and conflict are adequately protected, Ban extended his heartfelt condolences to the families of the victims and to the government and people of Pakistan.
Heavily-armed Taliban militants stormed the Bacha Khan University, named after the iconic Khan Abdul Ghaffar Khan, in Khyber-Pakhtunkhwa province yesterday, firing indiscriminately on students and teachers.
At least 20 people – 18 students, a professor and a staffer – were killed and many more were wounded in the attack.
PTI