This is why you need to pay attention to the technology choices that you make, and that your schools make. Chromebooks are designed from the ground up to be locked-down dystopian spyware once you "log in" to them with a specific Google account. For heaven's sake stop buying any more Chromebooks.
The correct solution here is not technological at all. Call into the school's board meeting during public comment, and make it loud and clear that the school is installing spyware on students' Chromebooks. Share your technical credentials and the method by which you found this. Emphasize stories of previous data breaches involving educational companies [1], and show officials that they are putting students' sensitive data at risk. (Edit: See the important point in the reply from 'n8cpdx below about the correct tone to use in your comments – don't repeat my words verbatim!)
The technical details don't matter too much to educational officials – as soon as the "Chromebook = bad spyware" label sticks and they think that a fuck-up here could cost them them bad press, they will allow their IT department to make more privacy-respecting technology choices even when those choices cost a little more. If no one speaks up, it's a race to the bottom driving us closer to the fiction in The Right to Read [2].
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[1] https://techcrunch.com/2021/11/22/smarterselect-exposed-mill...