what not to say to your child's teacher

Parent: "He's in your classroom. You do what you have to do."

It is theoretically possible to make that a supportive statement to a teacher in the context of a larger conversation. But when that's the entire response you give to me in the phone conversation* about your child's (mis)behavior in my class, it DOESN'T WORK AT ALL as a supportive statement.

*The word conversation implies that there are at least two people trying to, well, converse. Clearly this wasn't the case.

As is sometimes the case in phone calls or face-to-face meetings with parents, this explains SO MUCH about the child.