Good Question!

First thing this morning, a boy told me that another boy, "Alex," was singing and refused to stop. Apparently the singing--however muffled--was creating a distraction.

Here's how the matter was addressed from there:

Me: Alex, please stop singing.

Alex: I ain't singing.

Me: [with emphasis] You aren't singing.

...pause...

Alex: Well, then why are you telling me to stop?