I believe I saw this somewhere between the mid and late 1980s.  Possibly very early 90s at the very latest.  Saw it on TV, so I’m not absolutely sure if it was a movie or TV show.  I think it was a movie, though.  There was a teacher sitting at his desk in front of a classroom of students.  For some reason, the teacher pushed a button, and a panel opened up on the front wall, exposing a video camera.  I think it was in response to suspecting that somebody was cheating or something.  Somebody in the classroom may have been fumbling with a cast on his arm, and may have had something hidden in it.  That part is fuzzy, but I definitely remember the video camera part clearly.   Any ideas?