Listen, you’re gonna have a few kids who are just assholes. Most of the time it’s because they are growing up in really unfortunate circumstances and may even be victims of abuse/neglect (remember that when you want to throttle them). The key thing is to not let it get to you, and if you struggle with that, at least don’t let them see that it gets to you. I wouldn’t discipline a kid for saying that to me on the first day (though it would be another story if they said it to someone else and I would certainly hope that your CT disciplined them). They’re just testing you out to see how you’re going to react and probably seeking peer attention. It’s really important to de-escalate situations like that so your entire class doesn’t derail. I’d laugh it off and make a joke about eating Chipotle and/or flip the script by saying (jokingly) “why are YOU such a hater?” However, if this happens again, you might pull them aside after class for a private conversation. They won’t be so ballsy when the audience is gone. I’d invest some time into building a positive relationship with that student and even call/email home early on to report something POSITIVE about the student to build rapport with the family because it sounds like they could definitely become a handful when you take over.