IQs need to be based on relevant experience to be accurate. An IQ test that focuses on agricultural data will be slanted towards those growing up on farms and have lower scores for those residing in cities.
The real problem isn't that their brains aren't capable - it's the lack of family structure and sense of responsibility that fosters actual studying and application of oneself.
The entire test could be written in Ebonics and deal entirely with ghetto scenarios. The results would be the same. Asians and Whites would do best.