Not entirely sure, but this might be part of the answer:
"Linda Gottfredson, co-director of the University of Delaware-Johns Hopkins Project for the Study of Intelligence and Society, told United Press International: "I recently converted Bush's SAT score to an IQ using the high school norms available for his age cohort. Educational Testing Service happened to have done a study of representative high school students within a year or so of when he took the test. I derived an IQ of 125, which is the 95th percentile." In other words, only one out of 20 people would score higher.
Another IQ expert, Charles Murray of the American Enterprise Institute, the co-author of the bestseller "The Bell Curve," came up with a similar result when asked by UPI. Noting that everybody except high school dropouts takes the PSAT when they are sophomores, Murray calculated from PSAT scores that "I think you're safe in saying that Dubya's IQ, based on his SAT score, is in excess of 120, which puts him the top 10 percent of the distribution, but I wouldn't try to be more precise than that."
It's from a UPI article from January of 2004. Written by Steve Sailer