(a)The number of persons originally enlisted or inducted to serve on active duty (other than active duty for training) in any armed force during any fiscal year whose score on the Armed Forces Qualification Test is at or above the tenth percentile and below the thirty-first percentile may not exceed 20 percent of the total number of persons originally enlisted or inducted to serve on active duty (other than active duty for training) in such armed force during such fiscal year.
(b)A person who is not a high school graduate may not be accepted for enlistment in the armed forces unless the score of that person on the Armed Forces Qualification Test is at or above the thirty-first percentile; however, a person may not be denied enlistment in the armed forces solely because of his not having a high school diploma if his enlistment is needed to meet established strength requirements.
An AFQT score is derived from the ASVAB(essentially the militaries' IQ test). IQ scores are based on a normal distribution of scores from the general population with a mean of 100 and a standard deviation of 15. So the 30th percentile represents an IQ score of 92 while the 10th percentile would correlate with an IQ of 81.
Very generous and wrong. Any psychiatrist would tell you to not practice, and a when not practiced it's a very useful metric. We couldn't make as strong hypotheses about the effect environmental lead had on earlier generations without IQ tests. We couldn't measure the very interesting trend upwards in IQ scores over time regardless of lead, which implies anything from a structural problem with the test to a real improvement in intelligence in the general population since the test's invention. We couldn't quantify the genetic or environmental influences on intelligence without IQ either.
It's like saying a psychiatric test for depression is bad because you can practice to know the answers a depressed person would give.