At what point does a boy become a man in our society
 

American society specifically...

shortly before he gets sued for child support...

When he scalps a white man & dons his first buffalo pelt

I'm sorry, I misread the question

I think that answer still works

Honestly, when he commits a crime.

Outside of that there is no clear delineation in our society between boy and male that's universally agreed upon. Hell, I don't even think people can agree on whether masculinity is an actual thing, which is sad.

You cannot put a general age on a personal milestone, its dependant on the individuals mentality and maturity.

Think about society and age driven milestones

At 14 you can legally work

At 16 ( and some odd months in some states ) you can drive with restrictions

At 18 you can buy tobacco and should be graduating high school and most of your license restrictions should be lifted and most companies with age restrictions should be able to hire you ( including most military outfits ) can go into some strip clubs and some night clubs but can't drink ... Legally make own decisions ( varies by state as well but this is the usual age ) unless emancipated previously ... charged as an adult for crimes which can happen as a minor if necessary but is set in stone at 18

At 21 you can buy alcohol

At 25 your car insurance should drop ( male ) and you can be elected to the house of representitives

At 27 avg age a women gets married

At 29 avg age a man gets married

At 30 you can be a senator

At 35 you can be vice or actual president

At 42 oldest any active military will take you ( varies for different outfits )


Society gives you the most at 18 but I think from 25 down is when the responsibility factor really starts kicking in

you are a man, when you can stand on your own and handle your responsibilities on your own.

you are a good man when you realize you are not.