Read a debate from Prospect Magazine: The Duel: Is there such a thing as correct English?
“Because a common understanding of what constitutes correct English does exist, those who use it incorrectly may put themselves at a disadvantage—such as when writing job applications, or in an interview.”
“We agree on one thing. It’s vital that children (and adults) be able to communicate fluently in Standard English. But you make the illegitimate further argument that “Standard English” is “correct English.” That is a mistake.”
“utility, not correctness”
“There remains a problem of perception of people whose grammar is sloppy because they have not been made to attune their minds to it, or who use words wrongly.”
“The task for language teachers and (on a less elevated level) usage pundits like us is not to damn non-standard dialects and constructions as “incorrect.” It is to educate children (and adults) in when these are appropriate and when they are not.”