This behavior tends to stop after high school. It did for me at least. I don't remember anyone making fun of me or saying stuff like this since. But it may also be because I have a mean resting bitch face and am generally intimidating. In such scenario, I'd answer with "What did you just say?" with serious demeanor to offer them a chance to backtrack and wipe the shit grin off their face. Respect is crucial in social interactions. Respect is more important than fluency. In the small off-chance they double down, all bets are off.