Cal. Education Code § 22602

(a) Any person who is not already a member of the Defined Benefit Program and who is employed by a school district or county office of education to perform creditable service on a substitute basis and performs less than 100 complete days of creditable service during a school year for one school district or county office of education is excluded from mandatory membership in the Defined Benefit Program. This subdivision shall only apply to persons who are employed to perform creditable service by an employer that does not provide the Cash Balance Benefit Program under Part 14 (commencing with Section 26000). (b) Any person who is not already a member of the Defined Benefit Program and who is employed by a school district or county office of education to perform creditable service on a substitute basis is excluded from mandatory membership in the Defined Benefit Program, and creditable service performed shall be subject to coverage by the Cash Balance Benefit Program pursuant to Section 26400 if employed by an employer that provides the Cash Balance Benefit Program under Part 14 (commencing with Section 26000). (c) The amendments to this section enacted during the 1995–96 Regular Session shall be deemed to have become operative on July 1, 1996.