Update: the counselor tells me the science department chair and the course teacher recommend auditing the course for no grade, no credit this semester, but if DS continues to attend class and do the labs in class (as he has been doing all year) he should be prepared for the AP Exam in May. He doesn't need this science credit to graduate, but the counselor did tell me that they would honor his taking our state's online course and applying the credit to his transcript, if the online school accepts him.
I am waiting to hear why they did not choose the alternate assessment option.
I think I'm going to cry.