Reply #34: And how do you tell whether someone can't grasp calculus, or simply can't concentrate on it...

[Solon]

because of an unstable home life? The problem with your whole premise is that you make it out to be as if intelligence is easily defined and measured, when that is NOT the case at all. Cognitive sciences are only beginning to grasp the nuances of mental development and learning in the brain, with the exception of those who suffer some type of traumatic brain injury or suffer from an inherited disability, at this point, we can't say that some kids are simply smarter than others, things are much more complicated than that.