old head on young shoulders

Translations
мудрость не по годам
She's only ten, but she has an old head on young shoulders.
Ей всего десять, но у нее мудрость не по годам.
Definitions
A phrase used to describe a young person who acts or thinks in a very mature, wise, or sensible way, as if they have the experience or judgment of someone much older.
Words
old

adjective
старый
head

noun
голова
on

preposition
на
young

adjective
молодых
shoulders

noun
плечах