Oh, no. No, they are listening every single moment. They just want you to think they are ignoring you.
I don't have any kids; I just remember being a teenager quite well. Your kids always know a lot more than you think they do, and you probably know less about them than you think, too. Just a caution.
I've often thought about if we had children how we would handle our relationship around them. I think I would just be straight with them up front, because that was how I was raised and I was always grateful to my mother for just telling me the plain truth about things. But I don't really know; I'm just speculating.