The school is effectively making the computer a terminal into their system. Their system, their rules.
I know the OP won't like this answer but the OP should buy their kid another computer for their non-school activities. Of course they could also complain to their school/district to change the polices. Personally, I'm used to it. I have a personal computer for my own use and a corp computer that's managed by corp and is locked down. I don't complain the corp computer is locked down (except when it gets in the way of doing my actual job). For all personal stuff I use my personal computer.
I agree with this. If you had an rdp / citrix / ssh session to your employer you'd expect them to control what's on the other end. A Chromebook on which you're using a work/school account is much closer to that experience than a PC, but with the lines unfortunately much more blurred.
Has it been, in this case? If a parent says 'I do not agree to this', then what? Will the school district swap the system out for one that doesn't require end users to waive their legal rights? Has that ever happened when a parent objected to one of these EULAs, even once?
This reminds me of Asimov's Multivac home terminals where every user, in the comfort of their home, could dial in a query on their computer terminal and the massive infrastructure which is the continental-sized Multivac computer will respond with an answer.
In this case the student is not the owner of the Chromebook. They need to disclose this stuff to, and obtain consent from, the parents before taking control of the device.
Nonsense. They were designed to implement required policies when someone logs into a managed domain. Unless you're logging into something like that (where disclosures have been made and consent has been obtained) then there's no "dystopian spyware" involved. Absent any domain management policies, Chromebook are basically fancy thin clients that make efficient use of web-based services.
That having been said, the OP either conspicuously failed to mention that such disclosures were made, or (and this I find to be much more likely) the school was dumb enough to think they don't need to disclose anything because like a lot of school systems, they have gotten the curious idea that they basically own the kids and that the kids have no rights whatsoever. Should that be the case I hope a judge spanks them soundly for it because yeah, they absolutely do need to disclose this stuff to the students or the first time there's a serious problem due to abuse of the monitoring system the school is likely to get very, very pantsed for facilitating child abuse.