@Esper
Unless your mother IS your teacher, and unless she played along. I had a lot of fun calling my mother Ms. (insert name) in front of my classmates and my mother happily played along. Ever since that, I become some sort of 'negotiator' whenever any other students has some business with my mother since she's infamous for being incredibly strict (even though she isn't).
It's been 10 years and there's STILL someone who's surprised that I'm her son.
@Chireall That happened to my sister, she had our mother as her teacher too (Although I don’t know for sure what she called her during class, but I know they had lunch together), sis was just a bit older than Chi (a year or two), back then. She was the boss of the class, no one dared misbehave to her (they feared her too, not sure how much). But that only lasted in her era, by the time I got to school, mom already changed schools for promotion...