17 U.S.C. Section 110 provides an exemption to copyright for instructors to perform or display copyrighted materials during face-to-face teaching activities.  For example, it is permissible to show a full-length motion picture in class as part of the classroom learning. Note, however, that this exemption does not permit copying or distributing a work -- only displaying or performing it during class time. 

To qualify for the exemption, the performance or display must be made from a legally-obtained copy.  Also, the exemption only applies for courses in nonprofit educational institutions. 

Also, as the title implies, this exemption applies only to in-person presentations.  Diferent restrictions will apply in cases of distance learning or virtual classrooms.  See Distance Learning for more information.