Dialects are varieties of a language that contrast in pronunciation, grammatical patterns, and vocabulary and that are associated with geographic area and social class. All dialects, whether considered standard or vernacular, are regular. Years of sociolinguistic research have shown that dialects are merely different from each other. Standard English is a useful construct, especially for education, but it encompasses a range of dialects. A formal standard variety of English, as reflected in dictionaries and grammars, is associated with written language, but it is unlikely that anyone speaks it.
Speech communities use an informal standard that is a more flexible variety.
Standard English in the United States contrasts with Standard English in Britain, Ireland, Australia, or India. In fact, there is no single standard. Members of a speech community have a generally shared understanding of Standard English for their group. This is the dialect that is associated with educated people and good jobs, the one that schools are expected to foster. It is important to keep in mind, especially in the context of education, that linguistic features associated with vernacular dialects are not incorrect.