I would keep in mind that even Blacks who are in the middle class still deal with the ever-lasting effects that have been passed down from generations of racist experiences. Regardless of how much money is involved, minorities in this country still have various disadvantages, through no fault of their own, that can be exhausting to deal with.
I am Black and I grew up in a very poor neighborhood. My school was in a suburban area, and it was about 50% white, 50% Black. I was able to work hard, take advanced classes, and graduate in the Top 5% of my class, even ranking higher than most of my suburban white counterparts. Family structure and personal motivation also play a huge factor beyond just race.
I think - and I am speculating here, as I teach in a very white school - that it may have something to do with role models. When students think about who to look up to and who they want to be, there are racial differences in the way they answer those questions.
As a society we've been working since the 1950s to get more gender equity in advanced programs in math, science, and engineering, and that is still a work in progress. Racial equity will unfortunately be just as slow in coming, and that is a shame.
I can only agree with the two previous posters. It is just one more element of the achievement gap that remains the most pressing problem in education today. One element I would add is that my wife and I taught in two schools in an area where school districts had remarkable racial disparities. The school I taught in was majority white, and offered more than ten AP courses. The school my wife taught in was majority black (almost 100%) and there was just one AP class offered in the whole district. The good news is that many charter schools that serve minority students make a point of offering AP courses. Overall, however, given the importance of AP classes in getting in college these days, this problem is a very serious one.
I wish I could tell you that your observations were wrong. They aren't. It is largely a matter of class, not race. Those in the upper classes have access to the resources that help them succeed, including family members who have the skill and social capital to push AP and accelerated classes. At the same time, in this country we do not have equal access to the upper classes in all races. You are right that suburban school districts often have fewer minorities in advanced classes. They have fewer minorities in middle and upper classes.
I found this article from The Journal of Blacks in Higher Education interesting.
As the article notes, there has been an increase in the number of black students in AP classes, but there is still a disparity in the success rate of different students.
Traditionally, most participants in the AP program have been concentrated in the high schools in affluent, predominantly white suburbs of major cities. Also, in many racially integrated high schools, large numbers of black students have not been sufficiently prepared to take on the AP curriculum. (para 9)
If the students do not have access to the same preparation, and the same support system, they cannot be as successful. This is where we need to focus our efforts. Black children are just as smart as others. The schools they attend and the neighborhoods they live in are often barriers to their success.
As a country, we need to stop accepting the status quo. It cannot be all right to siphon poor children in the ghettos into gangs and prisons, instead of colleges.
For more, read here: http://www.jbhe.com/features/59_apscoringgap.html
And here: http://professionals.collegeboard.com/data-reports-research/ap/nation
Citation: "More Blacks Are Competing in Advanced Placement Programs, But the Racial Scoring Gap Is Widening." More Blacks Are Competing in Advanced Placement Programs, But the Racial Scoring Gap Is Widening. Journal of Blacks in Higher Education. Web. 07 May 2012. <http://www.jbhe.com/features/59_apscoringgap.html>.
If we knew the reason for certain, we'd have fixed it already. Don't discount past discrimination and stereotypes as a cause. They could very well still have an effect. For example, we have the stereotype that Asians are good at math and we have the stereotype that blacks are generally not great in school. Reserach has shown that people tend to live up to stereotypes about them. They (without being conscious of it) internalize the stereotypes and those stereotypes then affect the way they see themselves and the way they behave.