Why did the reading examination end up a disaster for Liesel?

Liesel wants to prove herself, she is aggressive when it comes to her education. All Liesel can do is recite a passage from The Grave Digger's Handbook which stands out in her head. It's a passage about how to bury someone when it's snowing. She recites the passage for the class and although Sister Maria isn't impressed, Liesel completes the task.