California Code, Education Code - EDC § 46142

(a) The minimum schoolday in any junior high school or high school described in Section 46141 may be computed by determining the number of minutes of attendance in any two consecutive schooldays and dividing that number by two. If the resulting quotient is 240 or more, the pupils shall be deemed to have complied with Section 46141, even if the number of minutes attended in any one schoolday is less than 240, but not less than 180.

(b) No computation authorized by this section shall result in any increase in state apportionments.