It has been shown that the average amount of questions answered correctly on IQ tests have almost doubled since the time when these tests were first being administered. The reason is debatable, but it no doubt has something to due with environmental differences between the early 20th century and today. People who grow up in impoverished environments are less likely to succeed, and they are will have less ability to develop their intellectual abilities.
Success and failure is contagious. If a person grows up around people who are poor and uneducated, they are likely to follow suit. If they see people similar to them on tv and in movies being portrayed as second class citizens, they are more likely to play those rolls in society. If people of other groups consistently see another group in inferior positions, they will think of that group and any individuals of that group that they encounter as inferior.
The only way to elevate a group from this status quickly is to give them a leg-up--to give them some degree of preferred status until equality is established. Unfortunately, this means that sometimes people of other groups will in turn be put at a disadvantage. But this will soon be balanced out as equality is established and pressure starts to come in the other direction; to be more specific, when whites start to sue and win in court for discrimination, etc.
As to the question of whether there are differences in the intellect between races. I would say that not enough research has been done to adequately answer this question. You would have to design a series of tests that measure multiple forms of intelligence and factor out cultural differences. I agree with the original poster that this kind of research would have to overcome a mountain of political obstacles. The researchers would no doubt be ostracized. And it would be of limited value. What would we do with the knowledge that Asians are 2% better that whites at mathematics?