Exceptions for educators to the exclusive rights of copyright holders to consider:
"...for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research..." (http://www.copyright.gov/title17/92chap1.html#107)
"(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."
Fair Use Frequently Asked Questions from Teaching Copyright
Fair Use Evaluator A tool to help you evaluate whether your use falls under fair use.