I don't think they're beyond question. Certainly, there's room for improvement (the cutoffs are too low. A physics PhD program isn't really interested in a test that has no measurement value for IQs over 120, or wherever it is -- and the analogy section was pretty g-loaded, so it's a shame that's been removed from the SAT, too). And schools don't just rely on standardized tests; they'll look at outside achievements, school grades, and maybe essays -- a competitive program might want people in the top 5% of intelligence, determination, and charisma -- which still means their students' academic test scores will need to be in the top 5%.

2) That holds true for studying results within schools, but not for test results overall. This is because schools admit people with roughly the same ability -- so they might have one person with test scores .5 stdev below the mean, but with a really brilliant essay. Fortunately, you don't have to take my word for it -- just look at the dropout rate among people who are admitted despite lower test scores and lower grades: http://www.capmag.com/article.asp?id=1635