Yesterday, I told my son that he had been progressing more slowly than any other student I had taught. The reason was that he had not been listening carefully and his marks were the lowest. Disputing me, he dared me to give everyone a truly challenging test. Further, he offered me this deal: if he scored second highest, I would have to take my words back. I agreed. The upshot is that he won the bet. His score was the second highest! Molly, never tell someone they are "the worst". It is too harsh. Also, if it were true there would be nothing they could do about it. Accuse them of something milder, less humiliating, and from which it is possible to recover.

Yesterday, I told my son that he was the worst student of all the students I have taught. The reason is that he never listens carefully and gets bad marks. He didn't agree and asked me to give them all a real test, if he got the second best score, I would have to take my words back and so I agreed. The result is that he got the second highest score. :-)