Tall people have tall kids and short people have short kids.
Height is a discrete, measurable quality that varies on a continuum. The offspring of tall people on average tend to be taller than the average of the offspring of short people. But there are many environmental factors that influence this. Nutrition is key, and even identical twins will differ greatly in height based on differences in nutrition during growth. And each generation tends to be taller on average than the last, possibly due to changes in nutrition and health care, though opther factors may be involved. So while you are right in a very general sense, the analogy doesn’t work.
Intelligence is a vaguely-defined quality. IQ measures something, though there is much debate about exactly what. Most people associate intelligence with verbal ability, information processing speed, ability to integrate data. We know VERY little about how this works in the brain, and less about the genetic vs developmental vs environmental factors that determine it. I always got credit for more intelligence that I probably deserved in school, due to my verbal skills, but not from my math teachers, who couldn’t understand how I could be “so smart” and still fail their classes repeatedly. You, I’ll bet, get less credit for intelligence than deserved when talking to some people in America because English is not your first language. So before we can make broad statements about smart and dumb people (or educated and uneducated, though I think since you’re talking about native ability you really mean smart/dumb or something like that), and their resultant socioeconomic, witgh all the tremendous and mostly negative social/political implications of such generalizations, we should have a better understanding of what we’re talking about. Yes, all mental ability rests in the brain, but that by no means implies a simple or straightforward relationship between genes and mental ability.
For some reading in this area, you can try Stephan J. Gould’s Mismeasure of Man, http://en.wikipedia.org/wiki/Inheritance_of_intelligence , and other general articles on intelligence and IQ. Interestingly IQ (which, I stress, is not synonympous w/ intelligence nor necessarily an accurate measure of it)IQ seems less inheritable the younger the person in which it is measured is when tested. In other words, IQ measurements of intellegince in infants suggest only 20% heritability, but in adults sometimes near 80%. Clearly there are dvelopmental and learning factors which may predispose to developing IQ during ones life, but only if environmental conditions are favorable for doing so. In any case, the question of the inheritance of intelligence is complicated by
1. not knowing exactly what “intelligence” is (excpet in the way, famously, we know what “obscenity is, i.e. we can’t define it but know it when we see it)
2. not knowing how to measure it
3. not knowing how the activity/structure of the brain constitutes the quality of intelligence
4. not knowing how genes influence the development of this activity/structure.
I’m not saying genes don’t play a role. They may very well play a strong one. I’m just saying that the simplified understanding I suggested above (smart parents=smart kids and vice versa) is misleading and more trouble than it’s worth.