I'm creating this spin off thread so people who have commentary about the "Just the Scores" thread can post here. I did not start that other thread, but I can see its OP's hope of getting just clean info on WPPSI scores is going to become harder and harder. Maybe the people who want to comment about WPPSI issues or otherwise analyze the scores can do it here instead.
As a start, here's my comment: I'm amazed just like many others here that there are so many super-high WPPSI scores. I'm sure a lot of it has to do with self-selection bias. People who have smart kids are more likely to sign them up for the WPPSI, people whose children scored highly are more likely to post about it on DCUM, etc.
I am trying to think of other ways to look at representative groups of scores, besides just asking people here to post them. I have not come up with much so far, but I did have one idea. NYC tests huge numbers of preK children each year for admission into the gifted & talented programs. As I understand it, the cutoffs are 90th percentile to be considered for District-level G&T programs, and 99th percentile to be almost guaranteed a spot. NYC uses the OLSAT for testing, which I believe is pretty similar to the WPPSI. Here is are link to some statistics on OLSAT scores for NYC preK students:
http://schools.nyc.gov/NR/rdonlyres/35EFC620-DB98-4A85-B218-066C1D44FD2E/0/2004YOBGTHandbook.pdf (page 7).
14,088 preK students took the test for the 2011-12 school year. I'm not positive, but I think there are about 75-80k students per grade, so that's about 18% of the potentially eligible students taking the test. 4028 of the test takers scored above the 90th percentile, so that's about 29% of those taking the test, or about 5% of the total students in the grade. 970 of the test takers scored at the 99th percentile, and that's about 7% of 14k test takers, or 1% of the total grade.
Those figures seem statistically logical, which suggests to me that NYC's OLSAT is a decent snapshot of where those kids are at the moment. I'd like to assume the same holds true for the WPPSI in DC, but I suppose that's debatable.