Fair use allows educators to make reasonable use of copyrighted material.
There are 4 factors to be considered to help determine fair use, they are: 1. the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes ; 2. the nature of the copyrighted work ; 3. the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and 4. the effect of the use upon the potential market for or value of the copyrighted work. More on the factors.
Columbia University's Fair Use Checklist can help you decide if your activities are within the limits of the fair use under U.S. copyright law (Section 107 of the U.S. Copyright Act).