You have made an excellent point that few people seem to have noticed. Many young black workers come across as sullen and hostile, but I have always felt that a lot of them are embarrassed and defensive. They know that they are hard to understand, they know that they come across as stupid to many of the customers, and they must realize that they are trapped in a world that is different from the world inhabited by their customers (black or white or Hispanic).
It's very sad, because of course their public image - which comes across as hostile and not exactly customer friendly - keeps them from making even that little personal effort that might have enabled them to jump over the years of lousy, separatist "education" they have received.
Heck, people can come here from Afghanistan (I'm thinking of some hot-dog vendors in NYC) without a word of English, and end up with a huge clientele that comes to their particular little hot-dog stand simply because they smile, if you're a regular, they know what you want on your dog before you even ask - and, of course, they're busy taking English lessons at night and dreaming of the day when they own their own little grocery store. These poor kids, on the other hand, are so sunk to the bottom that they can't even imagine fitting in or ever having a future.
This is funny, the Oakland school board, (not any great authority) passed this resolution as an attempt to get foreign language pay for their black teachers. (As the spanish speaking teachers did until the state passed an "English first" law doing away with the bilingual program in California). BTW, the new program is doing well and former spanish speakers move into regular english classrooms after one year. A proper approach might be to take these ebonics speaking kids and give them nothing but intense English for a year. Might do the trick.
You should hear blacks talk about the 'secret money' the Koreans or other internationals get when they come to this country. It's useless to tell them about the SBA (whose funds are available to legal immigrants) or the Asian family banks where family members pool their resources so others can open businesses, etc. To hear the average black tell it, the US govt is meeting these people at the airport w/a big check. Meanwhile, the Korean grocer in my old Philly neighborhood worked 7 days a week and slept in the store during snow storms so he could be open when other stores were closed. It takes hard work, not a handout from the government, and many blacks never make the connection.
Why the black churches haven't set up something similar to the Asian family banks is beyond me. There could be black-owned businesses in every black neighborhood if that's what they really wanted.
I have several advanced degrees and am often the only black person at conferences, classes, etc. I fail to see how teaching Ebonics is going to produce more black lawyers or PhDs or anything else except more welfare recipients.