Read about James Tate.
He left school at 14 but was working as a clerk when he lied about his age to join up.
Read his letters. Highly articulate and literate.

He was eventually sent back from the front because of his age, but he rejoined when he was old enough.
http://www.bbc.co.uk/history/worldwars/wwone/humanfaceofwar_gallery_08.shtml

The Daily Mirror, outbreak of war.
http://www.bbc.co.uk/history/worldwars/wwone/mirror01_01.shtml