In many episodes of the Leave It To Beaver Show, this has happened many times. In the earlier shows when they all live in the first house, the kitchen door is next to the front door. Every so often when they opened the kitchen door you would see a blank wall. Then other times someone would open the door and you see a kitchen hutch. They probably needed the kitchen set for the classroom scenes or other scenes. The director or others, should not have allowed the door to be opened so wide as to see the error.