I know this isn't a popular opinion on Hacker News, but why should there be any tracking whatsoever when using an OS? Are people saying that they're perfectly fine for their Windows/Mac/Linux distribution to track everything they do? The apps they use? The sites they visit? Because that's basically what ChromeOS does. It even tracks the documents you print to your desktop printer (routed through Google's cloud print service).
You aren't even anonymous when you use ChromeOS - you must be signed into your Google account. Just as a reminder, your Google account = your name, your date of birth, your location and optional phone number. In other words, some of your most personal and private information all tied to the activity you conduct on ChromeOS.
Google states that it does not read the content of your emails in GMail (emails are scanned by computer), but you could argue that your browsing habits are just as private and personal. No such assurances on how they handle this data. Does Google disassociate the identity of the user from their activity? If not, then who sees this data at Google? How long is this data kept for? These are important questions, but you won't find answers in Google's privacy policy. (And you're unlikely to find many in the tech community asking Google about them either.)
I would never recommend an OS that tracked the activity of students so relentlessly, especially when many students are too young to understand the horrendous privacy implications of using ChromeOS. Other companies like Microsoft are rightfully criticised for their tracking in Windows 10, yet Google gets a completely free ride. It's just baffling.