班主任就是容嬷嬷的替身
[bān zhŭ rèn jiù shì róng mā mā de tì shēn]
Refers to comparing a class advisor to 'Rongmummu,' the strict but well-meaning governess figure in the TV drama 'Story of Yanxi Palace'. It humorously suggests that the class teacher is authoritative and sometimes overly strict while trying to teach students the right ways much like how Rongmumu treats her charges.