Interesting, but you need to think harder - what is this study telling us about?
- The education level of high-school graduates?
- Or the education level of the subset of high-school graduates who seek to join the military?
They are different groups. The study looked at 350K high school graduates who applied to enter the Army between 2004 and 2009 and took the ASVAB. As the report acknowledges:
"The group is not representative of individuals across orwithin states and the nation, but is a self-selected sample of individuals aged 17-20, with a high school diploma, and an interest in joining the Army"
It is very likely that the subset has, on average, a significantly lower educational level than the superset.
Each year, about 2.75MM people graduate from high school. About 1.85MM (appx 67%) of them go on to college. The study group would have been almost entirely drawn from the remaining 0.90MM who do not go to college. Which means, more or less, the bottom third of the graduating high school class.
Any guesses as to the difference in grades, literacy, math skills, etc between the 67% of graduates who go to college and the 33% who don't?
http://www.edtrust.org/sites/edtrust.org/files/publications/files/ASVAB_4.pdf
http://www.census.gov/compendia/statab/2010/tables/10s0267.pdf
Sure, there's the occasional kid who was admitted to Harvard but chose to enlist in the Army and go to Iraq. There aren't enough of them to skew the above number.