Printing movie stills in high school newspaper

Understanding "Fair Use" of Copyrighted Materials
Although in most cases, you need to get permission from the owner of copyrighted material before using or reproducing it, Title 17: Chapter 1 § 107 of the United States Code does provide for special instances in which copyrighted materials can legally be used without permission from the owner.

Section 107, "Limitations on exclusive rights: Fair use," says in part:

The fair use of a copyrighted work ... for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include--

the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
the nature of the copyrighted work;
the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
the effect of the use upon the potential market for or value of the copyrighted work.
In other words, for certain nonprofit educational purposes a small portion of a film (for example, a still or clip) can be reproduced without first obtaining the permission of the copyright holder, but you should still give credit to and acknowledge the copyright holder as the source of the material.