Last December, when a student at Bolinas-Stinson School made a threat in class to shoot up the school, superintendent John Carroll said he knew “the kid personally and I dealt with it. Kids say unwise things sometime.” He contacted the Marin County Sheriff’s Office and deputies interviewed the student. “It’s a demonstration of how seriously we take this,” Mr. Carroll said. “We went through the protocol: searched him, interviewed the parents and searched the house…