From what I've seen, the bad effects don't necessarily just come from free access to the internet, but that everyone around them in their social group has a video camera that can covertly record, they're all immature children and thus you cannot slip up once or you get kid cancelled, and they start doing a collective dissociative freeze response in a self-imposed emergent panopticon as a result.

So if the teen phone turned into a restricted "call mom" device with no cameras and with neon yellow obvious fuck you coloring and a restricted set of apps, and police took away a full phone much like they take away cigs and beer it might be enough to break the critical mass to create this issue. They can have dedicated cameras for video club, use the family computer, have an xbox or switch and have whatever tech experience that millenials had, the last generation to not have exponential increases in anxiety , depression and sexlessness.

It's the covert camera + internet that it's the key issue.