Apologies, perhaps I'm being especially dense as my head's been total mush this 1st trimester - But I don't understand why though?
If the phone they have is not a smart phone and doesn't have the capability for apps/internet access, then where is the need to collect phones and limit screen time? Where do the misery and arguments come from?
As for 16 year olds, if they've gone out and gotten a job, saved and paid for a smartphone themselves (I can't realistically see a 14 or 15 year old having the self control/self discipline to save enough needed to buy one) then I don't see a massive issue?
All you can really do at that point aside from all the obvious parental controls that you can put in place (and that they will eventually find loopholes for) is just hope that they don't feel the need to keep secrets from you and make sure they know that not everyone is a nice person.
To never give people your personal real life information. That people will lie, will manipulate, will trick and deceive, will project their own thoughts/feelings onto others so they don't feel so alone, will bully, dehumanise, and so so so much worse.
You need to let them know that not everyone is a saint, there are some truly evil people out there and you have to be very careful where you tread as one person's dark sense of humour is another's legitimate sexual fantasy.
I knew all of these things at 16. Hell I knew all of these things by probably about 13. They'd drum it into you at school, after school clubs, whole PSHCE lessons dedicated entirely to this, as well as age appropriate tid bits of "be careful" at home from mum and dad.
But in this day and age of technology, all of that should be a given anyway :S
If your teen doesn't feel able to come and talk to you about things, that's the very first step in them falling down rabbit holes online.
All that being said, it's been a decently long time since I was a teen and since I was being warned about things by my parents and school, maybe things are really really different now and these warnings are taken forgranted. Maybe I really am just very out of touch and naive.
I just vividly remember being very conscious about not telling strangers anything about myself, and being very careful what sites I visited and feeling immense guilt to the point of nausea when I did something online I knew was "bad" or "wrong". Immense amount of fear and worry related to that.
It's a bit perplexing to me that seemingly this isn't a feeling kids these days have? Or if they do it's very fleeting because they know they can get away with stuff? Maybe?
I just genuinely don't understand tbh.