Under the carpet

Reilly goes to a preschool that looks like, or actually probably used to be, a split level home. The 3 year olds are downstairs on the front side of the house, the 4 year olds are upstairs and the 5 year olds are downstairs on the back side of the house. When Reilly has friends that are not in his area he says they "are under the carpet" aka downstairs.