Cal. Education Code § 52167

(a) (1) Except as provided in subdivision (b), in classes established pursuant to subdivision (a), (b), or (c) of Section 52165, not more than two-thirds nor less than one-third of the pupils shall be pupils of limited English proficiency. The remaining proportion of pupils in the class shall be pupils of fluent English proficiency. However, where there is documented evidence that these proportions cannot be met, the classroom proportions shall, at a minimum, reflect the proportion of the language proficiency classification for the particular grade level in the school and shall not result in segregation. Fluent-English-proficient pupils shall receive basic skills instruction in English and, to the extent possible, be achieving at the district norm. (2) In no event shall the primary purpose of the program be to teach a world language to English-speaking pupils. (3) The state board shall adopt any necessary regulations governing this section within 90 days after January 1, 1981. (b) The classroom proportion specified in subdivision (a) may be modified for the purpose of providing effective instruction for all pupils in core academic subjects. Pupils of limited English proficiency participating in programs established pursuant to subdivision (a), (b), or (c) of Section 52165 shall receive instruction for at least 20 percent of the schoolday in classes in which the proportions specified in subdivision (a) are met, and shall receive instruction in classes with pupils of fluent English proficiency for an increased portion of the schoolday, as their English language skills increase.