20-year-old Matthew Lane sent a text message to ABC News as his parents drove him to federal prison in Connecticut. "I'm just scared," he said, calling the whole situation "extremely sad."

Barely a year earlier, while still a teenager, he helped launch what's been described as the biggest cyberattack in U.S. education history — a data breach that concerned authorities so much, it prompted briefings with senior government officials inside the White House Situation Room. The breach pierced the education technology company PowerSchool — used by 80% of school districts in North America... [and operating in about 90 countries around the world]. With threats to expose social security numbers, da...