(1) The Bureau of Labor and Industries may by special permit authorize a child under 18 years of age to engage in employment otherwise prohibited by law if the child has successfully completed professional training for such employment conducted by any school district, or training that the bureau considers equivalent thereto, and the child:
(a) Has graduated from high school; or
(b) Is employed during such time as public schools are not in session for a period exceeding 30 days.
(2) The bureau or a person authorized by the bureau shall investigate periodically the conditions of the employment for which a special permit has been issued, to determine whether the permit should be continued.