Not only teenagers. I was 7 or 8 (~1990) when my dad told me not to use our home PC without his supervision and under no circumstances should I start Norton Commander. The next day when he was at work, I booted the PC, started Norton Commander (I observed that he typed 'nc'), and tried every possible function that I could find ;).
Also, today many more kids have computers at home they can mess with if so inclined. That wasn't the case back then.
These days it seems like anyone messing with hardware should have more than one computer.
Trying to get kids to Crouton on a Linux distro isn't necessarily practical, but the hardware is so cheap they can often get their own to tinker with at home. Apple and Microsoft products work to get you dependent and then strangle money out of you for as long as possible.
But from a software development perspective it's never been easier to write/run code in a web browser and doing something to your local computer isn't as important as making your computer do something.
iPads are definitely consumption oriented devices, and while I don't love Chromebooks, I don't think it's as dire as it seems.
You got the proportions backwards. It would be a few guys doing something weird that confuses the technically illiterate teacher and disrupts the whole class.
I'm all for hackable computers in schools but it has to be something that can be quickly restored to a known state and used as a dead tree replacement with zero fuss. This is why Chromebooks are owning this market.
Something like that, in 1996, which the IT teacher mostly tolerated. All we did was change the colour scheme and get to the programming tool the older students used. (I was 10.)