While there may have not been a lot of money ( or jobs ), folks in the 1930s
knew good entertainment. Actually spanking in mainstream movies, was not unique
but in a lot of films.
Here is clip from one I like, THE FOOTLOOSE HEIRESS, 1937. Starring as the lead
actress and spankee, Ann Sheridan. Good shot, horizontal body shot, where you
see her face. How real was the spanking, who knows, but it is a fun scene.