Pardon?

"Pardon?", accompanied by a cheeky grin. In fact, make that many cheeky and boyish grins from the 1 nensei. Whenever I go round checking their work, I would be greeted with many "Pardon?" when I try to explain to them their mistakes or talk to them. Sometimes the boys would anticipate that I'm going to speak and would go, "PARDON??" even before I open my mouth. Or they would shrug and say, "No, noooo wakaranai. I DON'T KNOW! or I don't speak ENGLISH! " after my conscientious effort to explain to them their mistakes. In their cheeky attempts to draw an exasperated look or sigh from me, they would shout, "PARDON??!" too when I speak to them in Japanese, refusing even to answer me in their native language. It's true when people say that boys are more childish than girls. Just look at the 1 nensei boys! The 2 nensei boys are equally guilty too!!