Cal. Education Code § 42238.51

(a) For purposes of paragraph (1) of subdivision (a) of Section 42238.5, 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 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 prior year, excluding the attendance of pupils in charter schools. (B) Compute the attendance of pupils who attended one or more noncharter schools of the school district between July 1, and the last day of the second period, inclusive, in the prior year, and who attended a charter school sponsored by the school district between July 1, and the last day of the second period, inclusive, in the current year. For the purposes of this paragraph, 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. The amount of the attendance counted for any pupil for the purpose of this subparagraph may not be greater than the attendance claimed for that pupil by the charter school in the current year. (C) Compute the attendance of pupils who attended a charter school sponsored by the school district in the prior year and who attended one or more noncharter schools of the school district in the current year. The amount of the attendance counted for any pupil for the purpose of this subparagraph may not be greater than the attendance claimed for that pupil by the school district in the current year. (D) From the amount determined pursuant to subparagraph (B), subtract the amount determined pursuant to subparagraph (C). If the result is less than zero, the amount shall be deemed to be zero. (E) The prior year average daily attendance determined pursuant to subparagraph (A) shall be reduced by the amount determined pursuant to subparagraph (D). (3) To the greater of the amounts computed pursuant to paragraphs (1) and (2), add the regular average daily attendance in the current year of all pupils attending charter schools sponsored by the district that are not funded pursuant to Article 2 (commencing with Section 47633) of Chapter 6 of Part 26. (b) For the purposes of this section, a “sponsoring school district” shall mean a “sponsoring local educational agency,” as defined in Section 47632. (c) This section shall become operative on July 1, 2007.