班主任比容嬷嬷还牛逼
[bān zhŭ rèn bĭ róng mā mā hái niú bī]
'Our class advisor is more terrifying than Grandma Rong'. Refers to the stern image of a strict class teacher who can be compared to the infamous nanny in an ancient drama series. 'Nanny Rong' is known for being strict and harsh, which symbolizes severity.