nobody's fooling this kid

Today, I co-supervised a contact between 5 brothers and sisters that are placed in separate foster homes. The eldest boy (9) said multiple times throughout the visit that I spoke a different language. I continued to tell him that I spoke the same language, but with a different accent. At the end of our time together, a worker at the facility began "hoovering" the carpet with the "hoover" while we waited for the child's taxi. I told the boy that I would say the man is "vacuuming the carpet with a vacuum." The little boy said, "see I told you you speak a different language!" What do you say to that?