This is a rather interesting orthographical note. Both "nought" and "naught" are correct alternate spellings of the same "archaic" word, but they have different connotations in modern usage. "Naught" is the British spelling and is also used by Americans when they are using it to mean "nothing" (as an attempt to emulate Shakespearian English). "Nought" is the American spelling and is still used today as a vocally shortened form of zero (distinct from that of 'o') in mechanical design, manufacturing, and military settings (among others), but not to mean "nothing".
The Nil in this really confused me and I put "You aren't just boys" thinking that we had gone to the negative. "There is nothing but boys in you" or "Not in you but boys" does help me see where the "nil" might have come from. How would you say "You aren't just boys" though? Just curious.