When my cp was in dance several years ago they had a 2nd, smaller dance room that had a door and a window. The window was in a horrible place for the dancers because there should've been a full length mirror there. I asked the owner about it and she said she was required by law to have the window there, or anywhere that minors are with an adult teacher.
Do rules like that apply to cheer gyms or was that merely because the dance room was a single enclosed room where there was usually only a single adult in there?
Come to think of it, I believe school room doors usually have a window in them but I also remember some teachers covering the window with construction paper because it was a distraction for the kids in class.