California Code, Education Code - EDC § 37617

The governing board of any school district operating pursuant to the provisions of this chapter shall divide the students of each selected school into as many groups as necessary to adequately accommodate a continuous school program so established and conducted.  Students of the same family shall be placed in the same group unless one or more of such students is enrolled in a special education class or unless the parent or guardian of such students requests that the students be placed in different groups.