(a) (1) 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 part-time basis for 50 percent or more of the time the employer requires for the full-time position shall become a member as of the first day of employment, unless excluded from membership pursuant to Section 22601.
(2) Creditable service in more than one position shall not be aggregated for the purpose of determining mandatory membership under this subdivision.
(b) Any person who is not already a member of the Defined Benefit Program and who is employed by a community college district to perform creditable service shall become a member as of the first day of employment, unless excluded from membership pursuant to Section 22601 or subdivision (b) of Section 22601.5.