Here is a situation that I have been in several times, but have only recently begun to give careful thought to. Suppose you are asked to teach a course that you have not taught before. A fairly common practice (at least where I teach) is to approach the colleague(s) who taught the course most recently and ask if you can adapt their syllabus (on the grounds that reinventing the wheel is in nobody's interest). In every case in my experience, the colleagues have freely given me not only their syllabi, but also their assignments, exam questions, and any other instructional materials that they used, and have given me permission to make use of them however I wish.
Of course being something of a control freak, I never use those materials without re-engineering them somewhat; like many (most?) academics, I feel the need to take ownership of the course by putting my own stamp on it. But I do usually take large chunks of those older course materials and incorporate them into my own. I suspect this is not uncommon (although maybe I am just wrong on this point).
It has only recently occurred to me that if one of my students did something comparable to what I do -- copy large blocks of text from somebody else's work and insert it into their own without attribution -- it would be a clear case of academic misconduct. And I would never dream of doing something like this in a work that was intended for publication. But somehow until now, doing this in a purely instructional context has always seemed innocuous.
So my questions:
How common is this practice?
Is it generally viewed as a form of plagiarism (and have I just been oblivious to something that should have been obvious to me all along)?
If one does make use (with permission) of a colleague's course materials, is there an appropriate way to acknowledge that? For example, by putting an "Acknowledgement" note at the bottom of the first page of the syllabus? At the very least, doing something like that would model good behavior for one's students.