A cyberattack has caused chaos for students at thousands of schools as they study for finals. The attack Thursday targeted a system that schools and universities use to manage grades, assignments and lecture videos. The hacking group named ShinyHunters claimed responsibility for the breach at Instructure, the company behind the learning management system Canvas. An expert says the hacking group posted online that nearly 9,000 schools worldwide were affected, with billions of private messages and other records accessed.