Whenever the area of adequate school construction existing in any attendance area is such as to prevent another attendance area from receiving the maximum area of school construction for each unit of attendance as specified for the district as a whole, the allowable building area may be computed separately for each attendance area. For the purposes of this section and Section 17041.5, an “attendance area” is defined as the geographical area serving an existing or proposed high school and those junior high schools and elementary schools included
therein.