California Education Code Section 48000

(a) A child shall be admitted to a kindergarten at the beginning of a school year, or at any later time in the same year if the child will have his or her fifth birthday on or before December 2 of that school year. A child who will have his or her fifth birthday on or before December 2 may be admitted to the prekindergarten summer program maintained by the school district for pupils who will be enrolling in kindergarten in September. (b) The governing board of any school district maintaining one or more kindergartens may, on a case-by-case basis, admit to a kindergarten a child having attained the age of five years at any time during the school year with the approval of the parent or guardian, subject to the following conditions: (1) The governing board determines that the admittance is in the best interests of the child. (2) The parent or guardian is given information regarding the advantages and disadvantages and any other explanatory information about the effect of this early admittance.