The United Nations found troves of rockets hidden in three UN schools since the conflict began. “We condemn the group or groups who endangered civilians placing these munitions in our school,” Chris Gunness, spokesman for the U.N. Relief and Works Agency, said Wednesday. “This is yet another flagrant violation of the neutrality of our premises. We call on all the warring parties to respect the inviolability of U.N. property.” Earlier this month, the United Nations also found rockets piled inside one of its vacant schools — near other schools used to accommodate displaced people. Inside a Gaza Strip mosque in...