Would this be considered a FERPA violation by a college coach?
1 attorney answer
Yes, it could be considered a FERPA violation. The coach is an employee of the school, and he publicly disclosed private information about your son's academic record.
However, what do you want to do about it?
The most reasonable thing to do would be for your son (since he is an adult and the claim is his, not yours), to ask to meet with the coach, go see him in his office, and explain that his comment seemed rude and embarrassed your son publicly, and you hope it doesn't happen again. If the coach acknowledges and apologizes, then the matter is over. If he objects or argues, then your son may have to take more formal action. He could report this to his supervisor, to the dean, to the registrar, or some other official at the school. Ultimately, he can file a formal report with the US Department of Education, Office of Civil Rights, but that seems extreme for a single outburst. For more information on that, see https://studentprivacy.ed.gov/file-a-complaint.
Be aware that this response does not create an attorney/client relationship. I live and work in Massachusetts and may or may not know the local laws where you live. I hope people find my responses not only helpful but somewhat entertaining as well. If you rely on this as legal advice, remember the old saying, "You get what you pay for."