A child who returns from school or play to an empty home, so called because the child must carry a key to enter the house or apartment. With the rise in single parents and working couples, increasing numbers of children fall into this category, often because of the inadequacy, unavailability, or expense of child care. If parents are obliged to leave their children unattended, though certainly not before age seven or eight, they should take great care to prepare the children to meet potential emergencies.