Morehead-Cain Recommendation

My son is nominated by his school and in the process of applying for the Morehead-Cain Scholarship at UNC Chapel Hill. They only allow one letter and say "“Choose the person from your school who knows you best. We generally recommend that your college counselor write your letter, but we understand that there are cases in which a teacher or administrator is a better choice.” Can anyone who has received this scholarship or at least advanced in the process tell us if this letter absolutely must be from someone at his school? He has an executive director of a big non-profit that he has worked closely with over the last two years that has written him a superlative letter that he would like to use if at all possible, but knows that following directions is the #1 thing. We just feel this letter would give the most insight into his leadership and character. Any guidance? Also, his public school counselor is new to him this year.

Hi, I am a hs senior self nominating. My counselor told me that she would write one if I absolutely needed her to, but she recommended I ask a teacher who has seen me in an academic setting. Hope this helps.