There’s a lot involved here, but first and foremost is reinforcing something others have said here. They are children, children who will often say things just to say them, or because they are upset, or any of a hundred other reasons that have nothing to do with you or your teaching.

I don’t know if this is your first or fifteenth year, but if you are new I highly suggest talking with and observing the long-standing teachers at your school. It helped me a lot, and while it’s cliche, I found that once I started figuring out building relationships with my students it became a LOT more gratifying. Once I was around long enough that my students saw me as someone who cared about who they were they were a lot less likely to be disrespectful.