Daily Chinese Idiom Guessing Game
Describes a huge difference or gap between two things; like the difference between heaven and earth.
壤地。天和地，一极在上，一级在下，比喻差别极大。
《抱朴子·内篇·论仙》趋舍所尚，耳目之欲，其为不同，已有天壤之觉（较），冰炭之乖矣。”
The performance of the two students was a difference as vast as between heaven and earth.