She's the teacher's pet.

她是老师的宝贝疙瘩。

《牛津词典》

Though she meant well, she was often chastised for being the teacher's pet.

虽然她是好意，可她因为是老师的宠儿而常被惩罚。

www.wizbcn.com

Eg. She never gets in trouble for not doing her homework because she is the teacher's pet.

他是老师的宠儿，所以家庭作业做不做都不要紧。

bbs.ebigear.com

But if Spain is to be the good pupil of southern Europe, it also wants to be teacher's pet.

ECONOMIST: The Spanish election