This question will have many answers and each one depending on who you talk to.
Personally, I have been told that wainscoting and chair rails along side a wall were mutually connected.
Chair rails were traditionally around 36 to 40 inches from the actual floor up the wall. This was to reduce the rubbing of the back of the chair on the wall. Then someone decided to fill in this space between the chair rail and the floor boards with paneling or wallpapering. Thus wainscoting might have emerged.
So, in my modest opinion, the wainscoting should fall within these parameters.
3/4 the height of the ceiling is WAY TOO high in my opinion.