There are situations where looked after/adopted children have parents/other family members contesting the decisions and looking to find them. There are situations where children have been/are being abused and the abuser is a parent who is looking for them, threats have been made re kidnapping etc. This has happened in a variety of schools I have worked in. You might just be doing urgent checking of emails or whatever but someone else might choose to be taking a picture and happen to get so,e other kids in the background, stick it n social media and there's an outside chance it could get back to the wrong people. There's an outside chance that someone else at pickup has there phone for nefarious purposes. Surely a blanket ban is easier to prevent this? I know it's only an outside chance but there we are, this is the currant school culture and these are the expectations imposed on schools from above, not from the schools themselves because they just love to think up new ways to upset parents.
It's a shame if parents don't like it but school's first responsibility is to the children, not the parents, and if for whatever reason the senior management team have decided that this is in the best interests of the pupils, or even just one particular pupil who may be going through something you can't imagine, then why is it so hard to accept that and trust that there are good reasons behind it?
Like I said before, where I work we are not allowed phones on in school at all, not at lunch or break time, not in the staff room or the office, just never. If we are waiting for an important call we can ask for permission to leave our phone switched on in the office and be notified if it rings. Does it piss me off that DP or family can't get hold of me if they need to, or just text to say 'we need milk' or whatever? Yes. Do I think it's a little OTT? Yes. But I accept that I'm not privy to every piece of information about what's going on in the school or why decisions have been taken.
And yeah, you'd think it was patronising for schools to have to tell parents to put the phone down and talk to their children, look pleased to see them, look at the picture they are so proud of or hear about the thing that really upset them that day. I think it's fucking awful that we have to. But we do have to. Year on year children come to us with more and more speech and language problems. We have children who do not know any nursery rhymes. Children who don't get a bedtime story. Children who don't know any traditional stories and fairy tales (apart from maybe the Disney versions in film form). Children who have never played a board game, or helped to bake a cake, or been to the bloody park. So we do everything we can to get parents talking to their children.
And of course neither safeguarding nor lack of interaction/neglect even is an issue in the vast majority of cases. But it will be for at least some pupils in every school. And schools can't just say 'please can only the good parents use their phones on site' or 'please can parents who can't be arsed to interact with their children collect from the no phone playground' so it ends up being a blanket ban. And as much as that might be a pain in the arse for you (generic you, no one person in particular!) well it's not really about you is it?