To be issued an esthetics license by the board, an applicant shall, in addition to satisfying the requirements of N.H. Rev. Stat. § 313-A:11, I(a), (b), and (e), have completed a course of at least 600 hours of training in a school approved by the board and have passed an examination conducted by the board. An apprenticeship approved by the board may substitute for the required training. Estheticians who have practiced professionally in this state for a period of at least 3 years prior to July 1, 1989, and who have satisfied the requirements of N.H. Rev. Stat. § 313-A:11, I(a), (b), and (e) and the training requirements of this section shall not be required to take the examination provided for in this section to be eligible for licensure under this chapter. Credit towards the hours requirement for esthetician training may be given to a licensed cosmetologist or barber for equivalent training in the cosmetology or barber program in a school approved by the board upon certification of the training by the school. Credit towards the hours requirement for esthetician training may be given to a licensed massage therapist for massage therapy training deemed equivalent by the board. Cosmetologists licensed by the board may obtain the training hours in subjects required by the board in increments at separate schools but must present certifications to the board for all required hours and curriculum subjects.