What is the difference between office=educational_institution and amenity=school or university?

A friend of mine works for a local university. One of his job is to ensure that rooms for lectures etc. are distributed sensibly among competing requirements (a popular course gets a bigger room, because more people turn up and a less popular course a smaller one, even though the same number of students might be enrolled).

I suspect that the intention of this tag was that, if mapped separately, the building he works in would be an "office=educational_institution" and the building with the rooms he books would be part of an "office=university".

However, looking at usage locally, it actually seems to be used as a bit of a catch-all for where other tags might not fit. For personal rendering purposes I just dumped it in a "nonspecific offices" category.

Also be aware of potential issus tagging non-campus and multi-site institutions. There's a local discussion of that here and here. While Cambridge is a bit of an exception where university tagging is concerned, multi-site institutions abound and so you won't get a one-to-one mapping of amenity=university to "real world university".