This cuts straight to the heart of most of us who grew up with prejudices based on speech. Accept two premises--that no single language/dialect is scientifically superior than another, and that humans unfairly rate a person's intelligence and status according to the social status of his/her linguistic group--and you must acknowledge that we as a society must eliminate the concept of "bad English."
Read why students must not be oppressed by inaccurate and offensive treatment by teachers who tell them they must "correct" any "non-standard" speech in order to be acceptable to academia. More clearly said--as soon as we tell children that they and their parents are stupid, we have not only passed on a lie, we have lost the war for their hearts and minds during the first skirmish.
The multiple authors in this collection show how we can celebrate bilingualism and allow proficiency in any dialect, (just as any modern "foreign" language) to prosper. Students are free to "code-switch" from one to another.
They make a convincing case that with such acceptance, students who are supported in their "non-standard" variety of English will actually grow to speak both versions better.