on-air television/video copyright

Could someone please send me the ruling about on-air/off-air television/video fair use copyright. A teacher wants to copy a copy of Oprah show to show to her health classes. I have a copyright request to send to Oprah, but I want the teacher to know about at home/at school video fair use. I can't find anything about video in my files and I an unfamiliar about the times and how many days a copy (under fair use) may be kept and shown. Your help please.

TIA Phyllis

     Phyllis Sigmond
     Library Media Specialist           "...I love the tracks of
     Lake Country School                    new thinking
     Hartland, WI  53029                    in my mind".
                                                  --Maya Angelou
     Phyllis[_at_]lcs.k12.wi.us



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