An idiom for deriving pleasure from another's suffering
We often experience the following:
We feel happy when our fellow classmates get a bad grade and not necessarily when we ourselves get a good grade.
We feel excited when our opposing team plays really awful and not necessarily when we our team plays well.
We feel pleased when one person we hate experiences some kind of misfortune and not necessarily when we ourselves get good luck.
What is a word or phrase to describe the phenomenon above?