Academics will be glad to know that there is a specific exception to copyright protection of materials to facilitate face-to-face teaching. (Note: this does not mean that plagiarism rules do not apply, so citation is still expected).
17 U.S.C. Section 110 provides that the following is not a violation of copyright: "performance or display of a work by instructors or pupils in the course of face-to-face teaching activities of a nonprofit educational institution, in a classroom or similar place devoted to instruction, unless, in the case of a motion picture or other audiovisual work, the performance, or display of individual images, is given by means of a copy that was not lawfully made under this title, and that the person responsible for the performance knew or had reason to believe was not lawfully made . . .."
Essentially, what this means is that you can show a lawfully obtained movie or image or project a page from a book for teaching purposes in a live, face-to-face classroom with your enrolled students. No specific type of work is excluded from this exemption, so, the House Report accompanying this section provides that you are "free to perform or display anything in class as long as the other conditions of the clause are met. They could read aloud from copyrighted text material, act out a drama, play or sing a musical work, perform a motion picture or filmstrip, or display text or pictorial material to the class by means of a projector." Remember, though, anything you perform or display must be from a lawfully made/obtained copy.
This does not cover online teaching, MOOCS, and the like. However, there is another provision of the Copyright Act that can apply to online teaching (although there are many additional requirements to meet for it to apply).
Regardless, classroom instructors who do not meet this criteria (such as online educators) or professors who wish to make a copy of a chapter of a book to distribute to the class, should still consider fair use if this particular Section 110 exception does not apply. Fair use may still apply to permit the use and that determination should still be made on a case-by-case basis.