(a) The holder of a valid designated subjects full-time vocational education, full-time career technical education, or career technical education teaching credential may, with his or her consent, serve as a substitute in grades 12 and below, and in classes organized primarily for adults, in technical, trade or vocational courses, including, but not limited to, agricultural occupations, technical occupations, or trade occupations which shall be part of a vocational education program. However, the holder shall not serve as a substitute for more than 30 days for any one teacher during the school year.

(b) The holder of a valid designated subjects full-time adult education teaching credential may, with his or her consent, serve as a substitute in courses organized primarily for adults. However, the holder shall not serve as a substitute for more than 30 days for any one teacher during the school year.