for one's age
年齢の割に背が高い。
He's tall for his age.
トムは年齢の割に小柄でした。
Tom was small for his age.
年齢の割に背が低い。
He’s short for his age.
彼は年齢の割には背が高い。
He is tall for his age.
トムは年齢の割に小さいです。
Tom is small for his age.