What do you call the action of putting their grades together like this, without the sentences you put after it? (this is the most important question of this comment).

Why are you stuck on “cannot” when the point of the idiom is about the (repeat pun) fruitlessness of comparing things by inappropriate standards?

You clearly can come up with a way to score a math test by the standards of an art class, but that is not typically a useful endeavor.