I remember it in black and white.  An mad scientist working for an old woman who runs a girls school.  He was working on switching brains of animals and people so they can live forever.  I remember he switches a brain of a girl and a cat and she climbs up on a gazebo and when someone tries to get her down, she scratches out their eye.  The school ultimately goes up in flames as I recall and the scientist (in the body of a dog) is running with the old woman (in the body of a cat) away from the burning school.  I really wish someone could tell me the name of the movie.  I think it might even have been a tv series movie or made for tv movie.  Still gives me nightmares.