SANA, Yemen — Airstrikes carried out by warplanes from a military coalition led by Saudi Arabia killed at least 19 people, mostly children, on Saturday in a residential area and a school in northern Yemen, witnesses and hospital officials said.  One bombardment in the village of Birken in the Razih District, near Yemen’s northern border with Saudi Arabia, struck the home of Ali Okri, a school principal, killing his wife and four of their children.  Then, in what has become known in the war here as a double tap, a second airstrike killed four more of Mr. Okri’s relatives as rescuers were trying to free them from the rubble.  In the Haydan District, another northern area, airstrikes on Saturday hit a school, killing 10 students and wounding 28 others, an official at a nearby hospital said.  When rescuers took the victims from the principal’s house to Shiara Hospital, which is supported by the medical charity Doctors Without Borders, staff members asked the rescuers to leave immediately, fearing that the hospital would be hit by another airstrike, rescuers said.  Several Doctors Without Borders hospitals have been hit by Saudi-led coalition airstrikes since the conflict began early in 2015. Saudi Arabia intervened in Yemen after Houthi militants ousted the country’s president.  Maj. Gen. Ahmed Asseri, the spokesman for the Saudi-led coalition, said the Houthi militants who dominate much of northern Yemen, including the capital, Sana, commonly station their fighters in schools and hospitals. But he said he had no specific comment on the airstrikes on Saturday.  “We all know that these criminal organizations and groups are under pressure of the government,” General Asseri said. “So they keep lying and saying that hospitals and schools are hit because they know the sensitivities of the international community.”  “They use civilian installations as the command and control centers of their organization,” he said. “Don’t focus on the technical details. This is a war. Collateral damage could happen, mistakes could happen. But we work in Yemen on behalf of the international community; we are in Yemen today because the fire is on our border. If we do nothing today, tomorrow all the area will be a failed state.”  Witnesses insisted that no Houthi military forces were present in either the principal’s house or the school.  “It’s a wanton aggression that can’t tell a civilian from a military target,” said Ismail Mufarih, a colleague of the principal, who helped rescue victims. “All were civilians. Their only sin was that they were Yemenis.”  More than three months of peace talks brokered by the United Nations ended on Aug. 6, and coalition airstrikes, which had paused for five months, resumed almost immediately, along with reports of civilian casualties.  General Asseri cited a recent report by the Joint Incidents Investigation Team, a panel set up by several of the coalition’s member states, which absolved the coalition of responsibility for civilian casualties in most cases, saying that Houthi militants often hid their forces in civilian sites.  In a post on Twitter, Doctors Without Borders put the number of dead in the attack in the Haydan District at 10 and said that 21 people had been wounded. “All were under 15 years old,” the post said.  Shuaib Almosawa reported from Sana, and Rod Nordland from Cairo.  A version of this article appears in print on August 14, 2016, on page A8 of the New York edition with the headline: 19 Are Killed by Airstrikes in Yemen. Order Reprints| Today's Paper|Subscribe
One bombardment hit a principal’s house, and another killed 10 students at a school, according to officials and witnesses.