글의 요지로 가장 적절한 것은? At school districts across the country, the chief technology officers responsible for safeguarding student data are tearing their hair out. Scores of education technology start-ups are marketing new digital learning tools directly to teachers－many are even offering them free to get a foothold in schools. That has enabled educators nationwide to experiment with a host of novel "adaptive learning" products, like math and foreign language apps that record and analyze students' online activities to personalize their lessons. But the new digital tools have also left school district technology directors scrambling to keep track of which companies are collecting students' information－and how they are using it.