Speakers of these "non-standard" varieties are routinely told that the way they speak is wrong, and ultimately inferior. (The prescribed form is the only correct form.) Invariably, they are expected to adopt the logic that success equates with learning to speak the variety of language typically taught in school.
As a result, many children who come from households where non-standard varieties of language are the norm are set at an immediate disadvantage; second-language speakers are daunted by adopting forms of language they do not typically encounter in their home communities--thus, feeling second class until they have mastered this task.
Invariably, some individuals become bidialectic (mastering two dialects), some become only marginally proficient in learning the standard (while eventually mastering the non-standard), while some will give in to the prescribed language premise, mastering the standard while rejecting the non-standard completely--often alienating themselves from friends and neighbors in the process.
The deciding factor as to which of the these three adaptive strategies an individual adopts is quite often a matter of overt "prestige" vs. covert "prestige."
Overt prestige is acquired by those speakers who have command of a standard dialect (or dialects) that is socially defined as that spoken to gain social status within the wider community; often that of the elite. Covert prestige, however, is that acquired by those speakers desiring to belong; to be considered a member of a certain community. And when the need to be recognized as part of a particular group becomes the deciding social factor, success is defined by the amount of "success" that can be achieved within a group vs. without. And in a very real manner of speaking, a nonstandard language--despite the stigma attached by the
References: Culture Shock, Michael Agar Linguistic studies, USF Related Articles: Fathers of Linguistics I Fathers of Linguistics II