What subjects are needed to become a soldier?

There is no specific subjects to become a soldier. You do have to graduate high school or get a GED and pass the tests they give you. They send you to schools for training and then you are sent to your duty post. I suggest you stay in school, learn to spell, and learn as much as you can. To be an officer you need a college degree, but just to enlist all you need is to be 18 and graduate high school.