The original link was from 2003 and I suspect that the composition of the military might have changed a bit since then.
Here's a link from October 2005:
http://www.military.com/NewsContent/0,13319,78111,00.htmlArmy Lowers Bar for Recruits
Army Secretary Noel Harvey and Gen. Richard Cody, the vice chief of staff, said Monday that the Army is using looser Defense Department rules that permits it to sign up more high school dropouts and people who score lower on mental-qualification tests, but they denied that this meant it was lowering standards
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maybe the dicipline of the military environment is helps these people to develop the basic skills that they couldn't or wouldn't in the public school system