The Fordham Institute reports on a new study that tracks individual, high-performing (90th percentile) students over time and checks on how many fall from the heights. The answer, according to Fordham, is that almost half descend from top decile performance. This is a very good study and I certainly recommend you read it.
Now for the whine. The Fordham press release exaggerates the results a lot. The press release says
The study sought to determine whether these “high flyers”—originally scoring at or above the 90th percentile—“maintain their altitude” over time? The answer? While most did, almost half did not.
The problem is that one would expect a fair number of students to drop out of the top tenth just because tests give imperfect results. The study authors understand this just fine. They explain that the reported 43 percent of elementary school math students who “descended” from the top tenth is really only 26 percent after adjusting for measurement error. So it’s more like a quarter of high flyers descended, not a half.
School reform is too polluted with hyperbole. So two cheers to Fordham for the good work but a couple of lashes with a wet noodle for the unneeded exaggeration.