Hello, school. Goodbye, smartphone. Across France, kids marked the start of classes today. But this year, they have to leave their mobile phones behind. Adopted several months ago, France has put in a place a nationwide ban on mobile phones for students in middle school and younger. High schools have the option of putting in place such restrictions. The ban includes phones, but also tablets and smart watches. Naturally, the rules have proved controversial amid ongoing debates about gadget addiction. French president Emmanuel Macron backed the law, arguing it would make students less distracted and motivating kids to engage in more physical activity. Maybe even talk to other students. But many school officials and critics have argued that the rules will be difficult to enforce on a daily basis, leaving teachers and school directors left with another burdensome task. And it’s not clear how the rules should be enforced: Whether phones must be confiscated at the start of the day, or whether they must absolutely leave them at home. Still, observers around the world will be watching the experiment to see if there are lessons for helping kids and parents strike a better balance between being digitally savvy and being addicted to gadgets.