An air raid on a rebel-held neighbourhood of Syria's northern city ofAleppo hit a school, killing at least 18 people, 10 of them children, Wednesday, amonitoring group said.At least one teacher was also among the dead in the raid on the Ansari district ofthe former commercial hub, the Syrian Observatory for Human Rights said. Rebel-held areas of the city have come under repeated attack from the air sincemid-December.The government's use of barrel bombs, unguided munitions generally dropped fromhelicopters flying at altitude to avoid ground fire, has come in for particularcriticism from human rights watchdogs.Because they cannot be directed against military targets, they exact anindiscriminate toll on civilians, which Human Rights Watch has said makes themunlawful. Source: AFP