What counts as Standard English will depend on both the locality and the particular varieties that Standard English is being contrasted with. A form that is considered standard in one region may benonstandard in another, and a form that is standard by contrast with one variety (for example thelanguage of inner-city African Americans) may be considered nonstandard by contrast with the usage of middle-class professionals. No matter how it is interpreted, however, Standard English in this sense shouldn't be regarded as being necessarily correct or unexceptionable, since it will include many kinds of language that could be faulted on various grounds, like the language of corporate memos and television advertisements or the conversations of middle-class high-school students. Thus while the term can serve a useful descriptive purpose providing the context makes its meaning clear, it shouldn't be construed as conferring any absolute positive evaluation.
(The American Heritage Dictionary of the English Language, 4th edition, 2000)