A system that thousands of schools and universities use was offline Thursday during a cyberattack, creating chaos as students tried to study for finals and underscoring education’s dependence on technology. The hacking group named ShinyHunters claimed responsibility for the breach at Instructure, the company behind the learning management system Canvas, said Luke Connolly, a threat analyst at the cybersecurity firm Emisoft. Instructure didn’t immediately respond to a request for comment or...