(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 full-time basis shall become a member as of the first day of employment, unless excluded from membership pursuant to Section 22601.
(b) Creditable service in more than one position shall not be aggregated for the purpose of determining mandatory membership under this section.
(c) This section shall be deemed to have become operative on July 1, 1996.