When I was 16 I was working at a grocery store and another worker around my age talked me into trying it out. I had heard of it from a high school class I had taken, so I figured I’d give it a try. I called him on the phone and he talked me through installing Ubuntu Dapper Drake on my laptop. The biggest issue back then was getting the WiFi to work, which required ndiswrapper to used the Windows drivers. We eventually got it working and then played Tremulous together.
I dual booted for a while, occasionally got angry at Windows and nuked the partition to go fully Linux. Occasionally got angry at Linux and nuked the partition to go fully Windows. Eventually settled fully on Linux. I did have a separate drive with Windows installed in my desktop at one point to play around with VR, but I’m not much of a gamer so the only time I use Windows now is in a VM if I need to interface with some device that only provides Windows drivers. Pretty rare at this point.
They could just disable booting from USB drives in the bios and password protect it. They could install something like Fedora Silverblue, or even customize the image used to include whatever modifications they want. Any changes they made to the image would be propagated through autoupdates. Kids wouldn’t have root, so they couldn’t forcibly install a different OS. Of course they could install flatpaks to their home directory, which is probably something administrators would want to prevent, but a knowledgeable student can always find ways to do what they want.
This of course requires schools/districts to hire people to manage that stuff, which could be a problem.