And, as I mentioned, our support is free, so there's nothing here for me except helping out someone that's looking for help. If you really want to use the Drive Trust Rules feature we can even help you out getting an extended trial (subject to approval) and the application to the beta program (also subject to approval), so that you can test this before committing to a paid edition.
Obviously, my opinion on this was more personal than technical. So, the "solution" will simply hide the problem.
In this specific topic, I simply believe that the things trying to be prevented can be achieved by students in a number of ways outside Google Workspace (therefore, without any control from the school). I do understand, however, that different companies/schools/domains have different needs, and I do not think that they are less important just because they are not my needs. My intention is always to help, not to create conflict - otherwise, I wouldn't be in this forum -, but I confess that I'm not in favour of any type of censorship. We are not a school indeed, but we have several EDU customers (in both free and paid editions), to which we provide free support, so Education is something we care about. And honestly, I can understand how someone favourable to the idea of this topic might be bothered by my comment. I guess you saw my comment more like bad criticism. It would only keep reality away from the school's control. Plain sharing prohibition would not solve the "problem". And the school can also let the students know that it has visibility over the things they think they're doing in secret, effectively discouraging them from doing it again, and creating an education opportunity about vigilance, privacy, and cause/consequence. And with those insights the school can define corrective plans and take measures based on actionable intel. It gives control to the school, which can use DLP rules, for instance, or the Investigation Tool, or even Google Vault, to monitor keywords and create a better understanding of what students are doing. In any case, students have plenty of ways to share thoughts and/or files outside the school's vigilance (they have dozens of messaging apps to do it) so maybe letting them do "inappropriate" things within the school's "realm" is not such a bad idea. When they are inventive and curious enough to find ways to achieve the results they want (especially when some users that use the same tools professionally fail to discover those same resources) they're showing resourcefulness and problem-solving mentality, which is a great skill to have.
The item that you see in Nautilus is ruled by the Online Account in Ubuntu Settings.