Pupils and teachers are returning for the first time to the school in the Pakistani city of Peshawar where more than 140 people were killed last month.
They will hold a ceremony to remember the victims of the Taliban attack.
Schools across the country are re-opening after an extended break prompted by the attack on 16 December.
The Pakistani government scrapped a moratorium on executions after the massacre and moved to establish military courts to try terrorism cases.
The Taliban said the attack - the group's deadliest in Pakistan - was in response to a government offensive in North Waziristan and the nearby Khyber area that began in June 2014.
The school killings were condemned across the world, with US President Barack Obama saying terrorists had "once again shown their depravity". The Afghan Taliban also criticised the attack.
Upturned chairs and blood stains the floor at the Army Public School auditorium the day after Taliban gunmen stormed the school in Peshawar - 17 December 2014
Parents have demanded assurances from the government that their children's schools will be protected
Security has been stepped up at schools across the country since the attack.
The government has ordered institutions to do more to protect schoolchildren and audits have been carried out on hundreds of schools since 16 December, according to Pakistani media.
Seven Taliban attackers wearing bomb vests cut through a wire fence to gain entry to the Army Public School in Peshawar in December.
They went from class to class, killing 141 people - 132 of them children - and injuring more than 120. All seven attackers were killed.
The school is near a military complex in Peshawar and many of the pupils that attend are the children of military personnel.
The city, close to the Afghan border, has seen some of the worst of the violence during the Taliban insurgency in recent years.
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