At least when I was in secondary school teachers did not have to confiscate phones, reasonable usage of cell phones was permitted (or laptops for that matter) while unreasonable usage would first result in the instructor asking you to put your phone away and subsequently result in confiscation. Reasonable usage could be using a English-French dictionary online, or taking a photo of a white board. I think it also helped that the school wifi blocked social media and the building had horrendous reception due to the building style, and most VPNs would be blocked so it was difficult to circumvent anyways. I think a complete ban is unreasonable, students should learn how to use technology effectively to ameliorate their education while also learning when it is not appropriate to use it at all (e.g. when the teacher is lecturing).

Edit: I should add for primary school I feel like devices are significantly less useful, and only school owned devices should be used under supervision of staff if necessary (e.g. a computer lab, or a chromebook cart). I do not know how many students bring phones in that age group now, since when I went the most anyone had was an iPod usually except for the rare person with more.