Here's the offscreen strapping scene from "Places in the Heart" (1984), starring Sally Field as a recently-widowed mother trying to keep her family together:
Since the point of that situation was how strongly disciplining her son affected his mother, I thought that the spanking should have been shown onscreen, with emphasis on both of their facial expressions, but the film makers apparently lacked the nerve to do so, even though by 1930s standards it didn't seem like a particularly severe punishment.
The boy had been caught smoking out behind the schoolhouse, I believe; his mother had to ask him how soundly his father would have strapped him for the offense, and he apparently gave her an honest answer.
His little sister sincerely asking him "Did it hurt?" afterward, that struck me as cutely naive of her...

--C.K.