a goody two shoes
A goody two shoes is a person who never does anything wild like partying, drinking, or getting in trouble, and usually hides behind a perfect grade or a perfect attitude.
My goody two shoes classmate never even goes to a party and gets straight A’s every year.
My goody two shoes friend acts like she’s perfect but is actually just hiding from her problems.
My goody two shoes brother never even eats candy and thinks everyone else is a sinner.