Cite the general statute. I looked up the bill everyone talks about that was passed last summer (S.B. 452) and this is the only reference to classifications pertaining to high school sports (found on page 29 of the document):
§ 115C-407.55. Rules for high school interscholastic athletic activities. Paragraph (5) "Administrative rules. – These rules shall govern classifications of schools into divisions and conferences, administration of games, and requirements for coaching, officiating, sportsmanship, and scheduling of seasons. The State Board may by rule delegate the authority to establish all or a portion of the administrative rules to an administering organization."
https://www.ncleg.gov/Sessions/2023/Bills/Senate/PDF/S452v7.pdf
It doesn't go into any more detail than that.