Syrian warplanes bombed a school in the northern city of Aleppo on Wednesday just as students were staging an art show, killing at least 19 people and injuring many more.

The missile that struck the Ain Jalout elementary school in the rebel-held east of Aleppo was among at least half a dozen bombs dropped as part of the latest battle between government and opposition forces for control of the city, making it unclear whether the school was deliberately targeted.

At least 10 of the dead were children, said the Britain-based Syrian Observatory for Human Rights. Activist videos posted on YouTube showed extensive damage to the school, part of which had been demolished, as well as collapsed classrooms and rubble-strewn corridors with Disney characters painted on the walls.

Another activist video posted on YouTube showed more than a dozen bodies laid out in zipped bags. There was also a video showing remnants of the students’ artwork. One painting featured a skeleton hanging over piles of skulls; another depicted birds as planes dropping bombs.

Hundreds of people — some say thousands — have been killed since the government launched an offensive to retake rebel-held areas of Aleppo last fall, including a sustained campaign of airstrikes, some of them using barrel bombs, that has leveled much of the city.

A recent rebel counteroffensive has intensified the fighting but not produced any clear direction to the nearly two-year-old battle for control of Syria’s biggest city and its commercial capital.

A day earlier, at least 14 students were killed in government-controlled Damascus when mortar shells struck a renowned Islamic school in the heart of the Old City.