We had a similar issue. DS began an AP Bio course last year using an AP prep book and an online course (hubby was his facilitator so the book and course were hubby's choices). While content was at the right level, the writing was too much for him to handle (he was 7.5). Like your son he could write but was reluctant to write a HS-required amount. In the end, he read the material and did well in the book's tests and online tests but he didn't hand up any written assignments or reports. He also didn't complete the course, stopping about 75% way through, because his interests changed and he prefered to spend more time reading up/ gaining depth of knowledge on just particular areas like psychology and diseases. We didn't sign up to renew the course this year.
I believe that what he really wants is depth so I am choosing to give him that by researching books for him to read. It isn't important to us at this point to record that he's completed HS-level courses. But the amount he reads may count for inclusion into a transcript...I'm still undecided on that. Good luck! I'd love to know how things develop for your DS as mine is in a similar situation.
