Kennedy didn't say anything. Nor did he react to the professor's remarks. He was much too used to them that they had completely no effect on him. Five years of that did that to a person. He positioned his cauldron correctly and said, "Scourgify." That had to do the trick. He then looked up and met the professor's eyes and said, "The five C's are: Cleanliness, color, content, concentration, and care." There.

After that, he pointed his wand at his cauldron and re-filled it with water with a simple Aquamenti, then casted Incendio under it. He was back up to speed. Following Professor Lafay's next instruction, Kennedy stood up to retrieve the ingredient from the cupboard. Then added the two cups of elf made vinegar into his water.

There, much better.