goody goody
[noun]
Synonyms: prude, bluenose, comstock, Grundy, Mrs. Grundy, nice Nelly, prig, puritan, wowser

[TahlilGaran] English Synonym Dictionary ▲

ˈgoody-ˌgoody noun (plural goody-goodies) (also ˌgoody-ˈtwo-shoes American English) [countable]
someone who tries hard to be very good and helpful in order to please their parents, teachers etc – used especially by children to show disapproval

[TahlilGaran] Dictionary of Contemporary English ▲

goody-goody
someone who tries too hard to please people in authority, especially teachers or parents.
Sandra's a real goody-goody - always doing extra homework and arriving early to lessons.

[TahlilGaran] English Idioms Dictionary ▲