Excellent subject and very nicely presented.  All this Nature vs. Nurture made me question the morality of labeling certain groups in the less intelligent column as somehow missing what I have observed in my almost 6 decades of life that those who are indeed "underprivileged" come with much baggage.  These children grow up in very unstable households, many missing one or even both parents, so no parent really has influence on these kids.  It is very important to address the fatherlessness in the homes and mom working so much she barely notices her kids.  Parents are so valuable in the rearing of their children that the lack of may be interpreted as a child's "g" factor being considerably lower, but in actuality these kids have the potential, but have never been encouraged nor have they had the mentoring to know how to succeed.