Re: how about a simpler system
"But with a PAYG SIM I can fire up a VPN/use a proxy and say goodbye to provider's restrictions. C'mon, teens nowadays do these things like breathing."
Go into any school IT technicians room, especially at lunchtime, and there's a constant stream of kids coming in who have forgotten their passwords, lost files, accidentally deleted files, had their passwords stolen buy other kids and any number of other "schoolboy error" they need help with. They know how to swipe their touch screens and use their apps, but you vastly overestimate the technical ability and common sense of school children. If it doesn't "just work", most of them will give up and move onto something that does "just work".