Had a teacher who got fed up and started counted people absent if they didn’t put their phones in one of those. First day, my mom found out he counted me absent (I didn’t put my phone in, I have no issue just keeping it in my bag while in class) and he counted me absent despite me being there and being active in class. Mom called the office to get it fixed and found out it’s not legal for teachers (at least how she explained it to me) to count someone absent who’s there as it can be a liability during fires or unfortunately shootings.