For the purposes of computation of allowances and apportionments from the State School Fund, whenever computations of apportionments based on average daily attendance are made for high school districts only the attendance in all classes of grades 9 to 12, inclusive, and in all types of ungraded classes, including classes for adults, which have been reported as attached to, or as a part of, a school which maintains any of grades 9 to 12, inclusive, shall be included.