The copyright case that was decided when the library I worked at felt they had to take copyright for class use seriously was Basic Books vs. Kinkos decision 1991 and a series of decisions that followed from it. That the use of the copyright material was for an educational purpose did not excuse Kinko's copying significant passages of books without payment of royalties.
Kinko's was a nationwide chain of copy centers often located near college campuses, and instructors would ask them to assemble course packs made up of copies of chapters from various books for the students to buy. Some publishers posted royalty rates demanding payment of a certain amount per page if copies were made, and Kinko's ignored it depending on the "educational use" test to save them.
fairuse.stanford.edu
Kinko's was a nationwide chain of copy centers often located near college campuses, and instructors would ask them to assemble course packs made up of copies of chapters from various books for the students to buy. Some publishers posted royalty rates demanding payment of a certain amount per page if copies were made, and Kinko's ignored it depending on the "educational use" test to save them.

Basic Books, Inc. v. Kinko’s Graphics Corp.
Plaintiffs in this case, all major publishing houses, allegeded that Kinko's infringed their copyrights when they copied excerpts from books, whose rights were held by the plaintiffs, without ...