Cool People You Should Know: Sean Reardon
How does the progress of initially high-achieving black and white students compare as they progress from kindergarten through 5th grade? It turns out that high-achieving black students fall back significantly more than low-achieving black students. For students who start school at the 84th percentile, black-white gaps grow twice as fast as students who start school at the 16th percentile. (See Reardon's paper here.)
The question, then, is why. Reardon suggests a few possible mechanisms, each of which deserve more attention in future research. The first possibility is an outgrowth of racial segregation. The average black high achiever attends school with lower achieving students than the average white high achiever. If teachers teach to the middle, high-achieving black kids may lose out compared to their white peers. A second possibility is that teachers treat black and white low achieving students similarly, but differentiate treatment among high-achieving black and white students. (This seems less plausible to me, but perhaps you have thoughts here.) A third possibility is that the home environments of high-achieving black and white students diverge more than the home environments of low-achieving black and white students.
Kudos to Reardon for putting this issue on the map, and may a thousand dissertations bloom.