Okay, but the potential harm / average good of internet access is orders of magnitude away from that of a firearm.

As a teenager, I would have loathed being restricted from the internet the way the above poster describes restricting their autistic teenager's.

(in fact, on one occasion my mother did restrict my computer access because I wouldn't go to the guitar lessons she paid for me anymore, I did absolutely loathe it, and I still consider that mildly abusive)

Actually from biological standpoint there are no clear lines between kids and adults. That distinction is post-industrial revolution cultural one.

There are no clear lines between summer and winter but sandals stop being appropriate footwear at some point nevertheless.

I’m not a biologist, but isn’t puberty still a thing?