This is a problem for sure. There is so much in this story I could comment on but I will just say that children definitely get an idea of what they are "supposed" to be from several different sources- parents, television, teachers, peers, etc. When you are young there is a sort of penalty for being different or unusual and children often end up gravitating toward some role at least some of the time. I think certain ethnic groups "over-achieve" and others "under-achieve" because of this pressure- they are just being who they are "supposed" to be. This is my verbose way of blaming the whole thing on peer and societal pressures.
People (adults and children alike) are not really equipped to resist societal pressure. We have a lot of things we are supposed to do- graduate high school/college, get married (maybe even to someone of our own race), have children, get a good job, shower everyday, wear "cool clothes", get good/bad grades, act black, act white and we often suffer societal consequences if we don't "behave"... I think the HN community, being more counter-culturalist/entrepreneurial than average can definitely see where I am coming from on this.