At the unofficial schools run by Syrian activist group Kesh Malek in opposition-held districts of Aleppo, the children don't go outside to play during breaks in case a barrel bomb should drop from the sky.
With 110 teachers, most of them new to the profession, the organization runs seven schools serving around 3,000 children in the divided and war-ravaged city.
Syria's largest city before the civil war, Aleppo is the scene of heavy bombardment as the Syrian army, backed by Russian airstrikes, tries to encircle it and wrest control of the rebel-held areas that are home to around 350,000 people.