Cal. Educ. Code § 42238.051

(a) For purposes of paragraph (1) of subdivision (a) of Section 42238.05, a sponsoring school district’s average daily attendance shall be computed as follows: (1) Compute the sponsoring school district’s regular average daily attendance in the current fiscal year, excluding the attendance of pupils in charter schools. (2) (A) Compute the regular average daily attendance used to calculate the second principal apportionment of the school district for the three most recent prior fiscal years, excluding the attendance of pupils in charter schools. (B) For the purpose of computing attendance for the three most recent prior fiscal years pursuant to subparagraph (A), the following adjustments shall be made: (i) For a pupil attending a noncharter school of the school district between July 1, and the last day of the second attendance period, inclusive, in the current, prior, or second prior fiscal year, who attended a charter school sponsored by the school district in the respective prior fiscal year, the amount of second period attendance generated by that pupil at the charter school shall increase the sponsoring school district’s attendance for the respective prior fiscal year. (ii) For a pupil attending a charter school between July 1, and the last day of the second attendance period, inclusive, in the current, prior, or second prior fiscal year, who attended a noncharter school of the sponsoring school district in the respective prior fiscal year, the amount of second period attendance generated by that pupil at the noncharter school of the school district shall decrease the sponsoring school district’s attendance for the respective prior fiscal year. (iii) For purposes of clauses (i) and (ii), a pupil enrolled in a grade at a charter school sponsored by the school district shall not be counted if the school district does not offer classes for pupils enrolled in that grade for the respective prior fiscal year. (iv) In each fiscal year, school districts shall report to the Superintendent the total prior year increase or decrease in second period attendance pursuant to clauses (i) and (ii) at the first and second principal apportionments. (v) For the 2022–23 fiscal year, an adjustment shall not be made to attendance in the second and third prior fiscal years. (vi) For the 2023–24 fiscal year, an adjustment shall not be made to attendance in the third prior fiscal year. (vii) Notwithstanding clauses (v) and (vi), if in any fiscal year the adjustments described in clauses (i) and (ii) result in a 50 percent or greater reduction of the school district’s second period attendance for the prior or second prior fiscal year, the school district’s average second period attendance for the three most recent prior fiscal years shall be zero.