It's not really enough to say that kids need to learn the standard without analyzing why such learning hasn't already occurred naturally. Surely you don't believe that millions of black kids simply refuse to learn the standard. There appears to be a need for something to bridge the gap from Ebonics to Standard English. Also, there are other things that need to be addressed, namely, racial attitudes and economic conditions that cause languages and dialects like Ebonics and even Spanglish to flourish.
Problems occur when the Ebonics speaking child enters the classroom and meets the Standard English teacher who has no idea of the features of Ebonics. Especially does this happen if said instructor is inclined to think that Ebonics is simply lazy speech. More often than not, she corrects the student's speech very frequently thereby creating a child who either begins to shrink back from participating or becomes hostile to the teacher or process. Or she stamps out his creativity with her insistence on his use of a language style he has hardly grasped as different from his own. In many cases, the child simply checks out from learning. How different it would be if students were shown the difference between the two languages first and then when correcting writing assignments the teacher were to first judge the ideas and style of expression and issue a temporary grade on that criteria alone; then ask the student to rewrite using standard rules of grammar as have been discussed and demonstrated in the classroom. This would be fostering learning in a positive environment and would facilitate greater reception to education and greater learning.
And Hmmmm, you are correct in saying,
As with all language, "improper" use of vocabulary or grammar can eventually become accepted ("aint" finally made it into the dictionary). I'm aware that ebonics has rules of its own, but I find it very difficult to believe that it was created by someone with an english usage textbook in one hand, and a swahili usage textbook in the other, who invented specific rules based on "African sounds and language structure."
True, no one sat down and intentionally created a fused language called Ebonics. It sort of began as an emergency language that took on greater distinction with the production of offspring who increased the vocabulary of said language, and with linguistic isolation.
However, what people did was 'gather' a number of people from different tribes on the West African coast who spoke different languages, threw them together on a ship regardless of whether they were friendly or feuding tribes, sold them to a new country with a host of new languages, denied them access to bilingual programs and formal education and then relegated them to the fields. African slaves formed an emergency language using a mostly english vocabulary layered on top of west african language structure necessary for the most basic communication with slaveowners and each other. In addition, after slavery was abolished, they were left to live on their own in isolated communities recirculating and expanding this language.
Yes, language is fluid but this is more likely to happen when languages come into contact. Observe the differences that exist in the varieties of English where there exist physical and even class barriers.