Unfortunately I don't have my copy on me so I can't look up the footnote in the back. IIRC it was the SAT, but I'm not entirely positive.
If you want to see something really telling about standardized testing though, check out this Greg Palast article on how the NCLB discriminates against minorities:
http://www.phillyblog.com/philly/nation/13968-no-child-left-...
Insulting question: I wonder if the authors made a certain specific error, when making said error implies the person is either ignorant, stupid, or intellectually dishonest.
I'm not not going to defend the statistic since I haven't seen the methodology. That said, I do think it's insulting to the authors to ask if they've made a very basic and specific error without first reading the methodology.
In any event, I'm sure you could email any of the authors and ask where the statistic came from if you are interested.
Thanks for the citation, but since I can't look up the book right now, perhaps you can answer a question. Is that really measuring the "average?" Or the average score of 13-year-old white students who are taking the test? That's a very biased sample; for instance, I took the test when I was 12 only because I seemed likely to qualify for the Center for Talented Youth.