an old head on young shoulders
US /æn oʊld hɛd ɑn jʌŋ ˈʃoʊl.dərz/
UK /æn oʊld hɛd ɑn jʌŋ ˈʃoʊl.dərz/

1.
少年老成, 思想成熟
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.
儘管她只有十歲,但她少年老成,總是提供明智的建議。
•
The new intern, though young, clearly has an old head on young shoulders, handling complex tasks with ease.
新來的實習生雖然年輕,但顯然少年老成,輕鬆處理複雜的任務。