If there's one thing I learned both as a kid and as a father, it's that restricting kids' access to computers - or anything really - just doesn't work: software solutions that exist for that purpose are almost always defeated by kids, who are reliably more clever than the adults who try to restrict them, and only exist to falsely reassure their parents.
If you're serious about controlling your children's cellphones, I'd suggest buying them Linux phones, or phones that you can install a mobile Linux distro on: nobody makes Linux apps, so good luck getting malware or shitty social media apps on them. And of course, you can keep the root password to yourself and set up your kids as non-privileged users.
Either that or feature phones - if you truly hate your children.
Good suggestions but I'm not convinced that's true.
It's certainly possible to lock some Android devices down hard without rooting them. See Samsung Knox as an example. Even a pro will have a hard time getting around that.
I trust my kids to mostly only use the devices how I say. The security is mainly to keep their mum happy and to keep them from spur of the moment bad descisions with their clicks and time.
No, I don't think it's unreasonable to have a technical level of control over young kids devices in partnership with close supervision. It's that or no phones until they're 16.