So my advice would be: Don't bother trying to provision a chrome-book to connect to some school network. Use a school-issued chromebook for school stuff (if that's what they issue...), use a normal PC for extracurricular learning.
For the record: my kids are in elementary school, and are issued lenovo laptops running windows. They are locked down to the point where they might as well be chromebooks; kids have unprivileged accounts and are allowed to run very few programs. This is as it should be; those computers are for a very specific purpose, and are not general purpose toys.
Indeed, when I was in school, the WiFi networks were very poorly secured, so it was easy for annoying kids to get their own computers onto school networks if other students were using school-issued laptops around them. Annoying!
If a kid wants to learn how to program, they're going to have to bring their own separate computer and it will be treated about the same as bringing their smartphone to class, i.e. not allowed except during very specific times, there would be concerns about liability of damage or theft from other students, and they probably wouldn't allow it on the school networks.
I see the problem with Chromebooks and cloud stuff more generally as being that it's difficult to see the productive use-case of programming outside just shuffling a bunch of data around. If your program's not actually doing something useful, it seems like it'd be difficult to imagine a career in it. -But if a kid can get a relay to trigger via button and then maybe via web interface and then maybe automate it, I think that opens the world of hacking up to them. You know, for $10, they can have a fully-solar (w/battery) thermometer or whatever they want -- the thermometer can feed a thermostat to energize a relay coil to start a heater or whatever.
-But I might be outlier, because in school we had robotics class a lot of kids were pumped for, but I was confused because we never did anything useful with them; it was more like an art class, except at least in art class we baked ashtrays for our parents. -But what am I supposed to do with a 5-watt robot that follows yellow tape?
It used to be that high school students were required to have a graphing calculator. These had to be purchased by the student (iow by their parents) and without factoring in 20+ years of inflation costed more than some Chromebooks available today. I suspect there were (and still are) financial assistance programs as i've known students living below the poverty line and they were able to meet that requirement.
Support costs, mainly.
A small school that does its own IT is more likely to be flexible.