or for college classes taken to fulfill HS requirements (which I realize is not the case here, but will not be obvious to the registrar).
Admissions does not deal with transfer credits. He should obtain a separate letter from the GC that he can present to the registrar. While it may all work out in the end, it will be infinitely easier for your son down the line if you can convince the HS not to list the course on the HS transcript.