My father's rural high school only went up to the 11th grade, so he graduated a couple of months after his 17th birthday. My grandparents refused to sign the enlistment form until he graduated (he was underage), so he enlisted in the Navy the day after his graduation. He was a fighter pilot in WWII.
Sounds like there were a lot of 17 year olds fighting like real men back then. Life and expectations were sure different. These days 17 year olds are only “teenagers” with 8 more years before their brains are “fully developed”, so they get a “pass” by society until then.