I've been working with the recruiters lately and I can answer your question. To get in the Army, you will need a diploma or a GED. A diploma will get you in just fine. If you have a GED, you will also need 15 college semester hours (basically one semester of college) before you can join.
That's how it is
"The best form of taking care of troops is first-class training, for this saves unnecessary casualties." Erwin Rommel