Notwithstanding educational requirements provided for in RSA 316-A:11, any applicant for license to practice chiropractic who matriculated in a chiropractic school or college between January 1, 1951, and January 1, 1968, shall be a graduate of a legally chartered or incorporated school of chiropractic requiring for graduation completion of a course of study of not less than 3,600 classroom hours in 4 academic years; and any applicant for a license to practice chiropractic who matriculated in a chiropractic school or college after January 1, 1968, shall be a graduate of a legally chartered or incorporated school of chiropractic requiring for graduation completion of a course of study of not less than 4,000 classroom hours in 4 academic years.