Just like the computers of yore, the screen is the family TV. And USB keyboard/mouse are a couple of dollars second hand - I'd bet if UK school districts are anything like the ones I worked with in my youth, they have rooms filled with peripherals waiting to be recycled.
I had forgotten about the TV! I imagine a lot of people will go that route to save the money on a new monitor.
Though, I think about the insane hours I spend tinkering with my computer when I was a kid and it makes me wonder how many parents would be happy to let their children go on tinkering for hours like that on the commong family screen!