This cannot possibly be true. School system are artificial constructions created by men to serve men. They are not given laws of nature. The only thing we can tell from the above is that the current school system does not serve well black Americans. School system should adapt to whatever the "cultural factors" of the populace they serve.
Whether this should be through prolonging schooling hours; providing stronger and more persistent emphasis in personal hard work; correcting a harmful self-image; getting rid of institutional racism; using different instruction techniques; or any other method that may addressed the "underlying factor" can only be discovered through research, experimentation and a willingness to change and adapt.
It is easy to find examples of a schooling that adapts to the unique circumstances of some children, for example: intense language training for children from immigrant families, schools at hospitals or schools that follow a circus around the world (http://www.guardian.co.uk/education/2007/jan/26/schools.uk).