Cal. Ed. Code § 52164
Each school district shall ascertain not later than the first day of March of each year, under regulations prescribed by the State Board of Education, the total number of pupils of limited English proficiency within the district, and shall classify them according to their primary language, age, and grade level. This count shall be known as the "census of pupils of limited English proficiency" and shall consist of a determination of the primary language of each pupil enrolled in the school district and an assessment of the language skills of all pupils whose primary language is other than English.
The census shall be taken by individual, actual count, and not by estimates or samplings. All pupils of limited English proficiency, including migrant and special education pupils, shall be counted. Special language assessment instruments, designated by the superintendent and in compliance with the requirements of subdivision (j) of Section 56001, may be used for special education pupils. The results of this census shall be reported to the Department of Education not later than the 30th day of April of each year. The previous census shall be updated to include new enrollees and to eliminate pupils who are no longer pupils of limited English proficiency and pupils who no longer attend school in the district, and shall be reported pursuant to Section 52164.1. Census data gathered in one school year shall be used to plan the number of bilingual classrooms to be established in the following school year.
Ca. Educ. Code § 52164