"His priority did not seem to be to teach them what he knew, but rather to impress upon them that nothing, not even... knowledge, was foolproof."
"It unscrews the other way."
"Well, we were always going to fail that one,"said Ron gloomily as they ascended the marble staircase. He had just made Harry feel rather better by telling him how he told the examiner in detail about the ugly man with a wart on his nose in the crystal ball, only to look up and realize he had been describing the examiner's reflection."
"Indifference and neglect often do much more damage than outright dislike."
"But Dumbledore says he doesn't care what they do as long as they don't take him off the Chocolate Frog cards."
"I’ll make Goyle do lines, it’ll kill him, he hates writing,” said Ron happily. He lowered his voice to Goyle’s low grunt and, screwing up his face in a look of pained concentration, mimed writing in midair. “I... must... not... look... like... a... baboon’s... backside."