"For me, kindergarten was a hard lesson in life of how badly behaved, stupid and lazy others can be. Quite the opposite of all that lovely sounding stuff about everything I ever needed to learn was in kindergarten."
Which would tend to indicate either that parents are doing a lousy job before they send their kids off to school. Which is why they learn it in kindergarten, if at all, by that time.
If the parents don't get them off on the right foot in the critical years between birth and kindergarten, it is highly unlikely, IMO, that kindergarten will make much of a difference for more than a few who haven't already been ruined/severely disadvantaged. But I also doubt that kids are born with all the tools they need to adequately function socially. Nature predisposes and nurture finishes the job, or not?

