don’t call it a failure of the public school system, call it an epic failure of democratic social, economic, and educational policies within the black community.
In analyzing that failure consider that a good percentage of aristocrats in Middle Ages were illiterate. Why did they never bother to embrace literacy, but found plenty of time to learn weapons? Because the former was irrelevant to them, and they could use someone else to do their paperwork for them. The latter was very much relevant - it is hard to depend on servants or city guards who are never there when robbers intend to take your life and your coins.
People who do not bother to study today do so in knowledge that these skills will not be needed. They do not expect to find a job; they do not expect to even look for a job. The only literacy ability they need is to cash a check. What do they study instead? We know what TM selected for his advanced education.