an old head on young shoulders
US /æn oʊld hɛd ɑn jʌŋ ˈʃoʊl.dərz/
UK /æn oʊld hɛd ɑn jʌŋ ˈʃoʊl.dərz/
1.
a child or young person who thinks and acts like an older, more experienced person
:
•
Despite being only ten, she has an old head on young shoulders and always offers sensible advice.
•
The new intern, though young, clearly has an old head on young shoulders, handling complex tasks with ease.