During the epidemic, schools were closed and classes were held online. Xiaoming's learning foundation is not good. How to say it in idioms?

Snow plus frost-aggravation

Pinyin: [Xu Shang JiāShuāng]

Source: Songshi Daoyuan "Jingde Dengchuan Record" Volume 19: "What makes you know is still too much."

Interpretation: Metaphorically, successive disasters make the damage more serious.

Synonyms: take advantage of the fire to rob/take advantage of the danger of others/add fuel to the fire/avoid the pit and fall into the well.

Antonym: timely help/icing on the cake/double happiness.