California Code, Business and Professions Code - BPC § 7332

(a) An apprentice is any person who is licensed by the board to engage in learning or acquiring a knowledge of barbering, cosmetology, skin care, nail care, or electrology, in a licensed establishment under the supervision of a licensee approved by the board.

(b) For purposes of this section, “under the supervision of a licensee” means that the apprentice shall be supervised at all times by a licensee approved by the board while performing services in a licensed establishment.  At no time shall an apprentice be the only individual working in the establishment.  An apprentice that is not being supervised by a licensee, that has been approved by the board to supervise an apprentice, shall be deemed to be practicing unlicensed under this chapter.