Goodgulf:
The thing is, the Beaver knew that it was possible. Even if Ward and June didn't spank him he knew that other parents spanked and that his could decide spank at any minute.
That's what made those scenes believable. You couldn't do the same the same scenes in a sit com today - they just wouldn't be believable.
There was a conversation within a fairly early episode of "Leave It to Beaver" in which the Beaver, having a heart-to-heart talk with his father, referred to how Ward "used to spank us when we were little," so clearly both Wally and the Beaver had been spanked at some point in their young lives.
The Beaver was only perhaps nine years old at that time, so by "when we were little" he probably meant when he was around six years old, the suggestion apparently being that his parents had decided to eschew the use of corporal punishment as a child-rearing strategy several years earlier.
This wouldn't have been all that unlikely in time context, since by the late 1950s numerous parents, especially middle-class ones, were influenced by the published child-rearing theories of Doctor Benjamin Spock, who discouraged the spanking of children in favor of other methods of behavior modification.
Still, AFAIC it's true that Wally and the Beaver, in having parents who eventually eschewed spanking their children, would've been in the minority among their age-group peers circa 1960... --C.K.