1. It's functional literacy at age group - not "unable to read Latin letters"

2. Ime, education in phonics honestly sucks and fails to take into account local and regional dialectic differences. Maybe treating AAVE (and other regional dialects, similar issues exist among White Appalachians in rural WV, TN, and KY for example due to the Scotch-Irish heavy register) as a second language might help bridge the gap.

Clarence Thomas is an example of that kind of issue - his first language was Gullah (a mixed creole between West African languages and English) and it has had an impact on his own education earlier in his career.