Notwithstanding Section 17017.7, the definition of “substantial enrollment” set forth in that section shall apply only to elementary and unified school districts. For a high school district, “substantial enrollment in multitrack year-round schools,” for the purposes of Section 17017.7, means that at least 30 percent of the pupils enrolled in the high school district are enrolled in multitrack year-round schools, or that 40 percent of the pupils enrolled in public school in kindergarten and grades 1 to 12, inclusive, within the boundaries of the high school attendance area for which the school district is applying for new facilities are enrolled in multitrack year-round schools. In addition, a high school district shall be deemed to have a substantial enrollment in multitrack year-round schools for purposes of Section 17017.7 if, at the option of the district, the entire high school to be constructed is to operate on a multitrack year-round basis.