Wis. Stat. § 106.025: Plumber apprenticeships.

(1) The department may prescribe the conditions under which a person may serve a plumbing apprenticeship, as to preliminary and technical college attendance requirements, level of supervision of an apprentice, the character of plumbing work in accordance with ch. 145, and the credit for school attendance in serving the apprenticeship.

(2) Every person commencing a plumbing apprenticeship shall enter into an apprentice contract under s. 106.01.

(3) After the expiration of an apprenticeship term, no apprentice may engage in the business of plumbing either as an apprentice or as a journeyman plumber unless the apprentice secures a journeyman plumber’s license. In case of failure to pass the examination for the license, he or she may continue to serve as an apprentice but not beyond the time for reexamination for a journeyman plumber’s license, as prescribed by the rules of the department.