I'd love to see the research on that - especially if you have anything that explains the lower IQ.
For those that may not realize it, 90 is the bottom of average, so if the AVERAGE IQ is 85, then it stands to reason that a healthy percentage of kids sitting in the regular classes have IQ's in the educable mentally retarded range - and these kids are expected to achieve at a level commensurate with those of average intelligence. What an incredible quandary for students and teachers. And unfortunately the tax payer. Because when these kids fail, and the schools fail then the tax payer is on the hook for whatever it costs to bring this kids to a average level.
Yes, it is more of a political than education problem. What community leader, representative, professor is going to announce that the average inner city kid is below average in intelligence and that the curriculum needs to be restructured with that in mind? Can't - it would be racist.
My direct link no longer works; however, you can get La Griffe du Lion and look down the left column. You will come to an article summarizing the 85 problem.