Assignments taken and re-used without consent
I am a professor in a UK university.  I would say that it is standard that if you teach a course and then hand it on to someone else then you should hand over all your teaching material, which your successor will typically modify to their taste.  Moreover, people do not usually keep track of authorship, except possibly in the case of a full set of notes that is similar to a book.  Of course it is polite for people to be open about what they are doing and to express appreciation for any material that they inherit.