SAO PAULO (AP) — Brazilian students returned to class this week with a new task: staying away from their smartphones under a new law restricting the use of devices in schools. The bill is part of a global trend for such limitations. “Students were having trouble concentrating,” school principal Meire Nocito said Thursday. The law applies to public and private schools, restricting smartphone use inside classrooms and the halls. Phones are still allowed for educational purposes, with the teacher’s permission, and schools have the autonomy to set their own guidelines, such as whether students can keep phones in backpacks or store them in lockers or designated baskets.