>the multicultural "whole-language" concepts, such as "Black English" and "Spanglish"<

I'm aware of Black English as a separate language/dialect/creole. I understand from something I read (perhaps Stephen Pinker's the Language Instinct) that it has an internal grammar as precise and consistent as standard English.
I'm not aware of Spanglish at all.
I grew up with something called Franglais - an unholy mixture of the two languages which required basic understanding of both to make sense of it, but as far as I'm aware that was only ever used humorously and I cannot imagine it was used in a school situation.

Enlighten me as to what the US school system means in practical terms by a 'multicultural whole-language concept' and I'll tell you what I think!