My school doesn't have a policy about teachers having to lock away phones, but I consider it unprofessional to have mine with me in my classroom. It stays in my office, and I check at breaktime or during my free periods. My DTDs are in Yr R, and if there is a problem (there has been twice), their school contacts my school and a message is brought to me. I see absolutely no reason why students should have to have their phone with them in lessons - if I can manage, so can they. In my VI Form lessons, we have a "phone box" and all phones go in there for the duration. With younger students, if I see a phone, I confiscate it and it goes to the school office for the rest of the day. If any one student has a phone confiscated more than twice, it is only returned to the parent, not the child.
Mamatomany - I think your attitude is awful. In the "old days" (ie when I went to school), there was no rule about schools having to let parents know 24 hours in advance. Detentions are supposed to be inconvenient. That is one of the points of them. I teach in a school where a great many parents have your kind of attitude and all it does is give kids the idea that they don't have to adhere to rules. That's not a great thing to teach children. We all have to follow rules. That's the way life is. And teaching your child that they don't have to is irresponsible and unhelpful. In pratice, I can't imagine that any school will keep a child in detention without letting their parent(s) know - the difference is that a school can contact a parents to inform them that their child will be kept in that day, rather than giving notice. Personally, I think that's a good thing.