" "Behold, verily, there is the woman of the scarlet letter: and of a truth, moreover, there is likeness of the scarlet letter running along by her side! Come, therefore, and let us fling mud at them!" - Nathaniel Hawthorne The Scarlet Letter - Chapter 7
Okay, seriously, who in their right mind says something like that? These characters were CHILDREN, nonetheless!
What did parents teach their children back in the day??
What could be the importance of having children speak this way? Perhaps, in making the children of the village speak in such tongues, Hawthorne is showing that Pearl's childish behavior and her unique personality is supposed to be taken as unusual and a sin. Pearl is, after all, the result of a "sin" committed by her mother, Hester, and the local priest, Dimmesdale, so perhaps her strange elvish behavior is one way that Hawthorne shows the breakage of society's standards.

I think Hawthorne is trying to prove a point having the village children speak so proper and unchildlike. Pearl is the free spirited "wild child" that breaks all the rules of Puritan life.
Perhaps this is true, but maybe could the reasoning behind it also help to intensify the emotions that Pearl leaves on the reader with her reaction to the children? It almost seems like depicting the children as small adults in this society helps to bring out Pearl's unique behavior.
What if this is an omen for us nowadays? Perhaps Hawthorne saw this adventure as a possibility for the future of America? Perhaps a different time, a separate religion, even a better life than the one Hawthorne's people would have to live through.
Maybe Pearl is instead of being treated like the wicked bastard-child we know her to be, is instead the common link in all of us....part caring, religious and part prideful pariah.
That sounds like almost every child I have come in contact with, lol.
Yes, this one always makes me chuckle. I do think it's fair to note that if kids grow up hearing their parents talk that way, then they will, too.
Novelists were not, at this time in literary history, trying to record exactly what characters sounded like -- the speeches of the adults are also more dramatic, more elevated, more well-crafted than everyday speech. I suppose Dimmesdale as a preacher would have had training as an orator.
Anyway, Mark Twain was unusual for his attempt to write down regional dialect, recording the way they sounded to outsiders.
Oh I think we are suppost to believe that those children know what that "A" stands for and that Pearl is a bastard child, really? would kids even care? I can see the kids picking on Pearl in a different setting but to stop playing and fling mud, that is real fiction