Bothered

This happened over a week ago, but it's been really nagging me. My mum had a dinner party and invited some people over, including my old violin student from 6 years ago. He's now a freshman or something in high school. When he got to the house, I went over and waved and said hello. Instead of saying hello like a normal human being, he decided to say, "My violin teacher says that you were a bad teacher." O. Um. O.
Granted he was really the first student I ever had, so not everything was perfect, but...why would he say something like that?