On the road, so this will be short. I'll try to come back with more if I have a chance.
Your consultant is correct about losing a year of services. To age 21 typically applies to those who have not accepted/earned a high school diploma. But then, if she's met diploma criteria, presumably she won't need the services, or will have graduated to accommodations only.
I agree that there are advantages to collecting some ELA and social studies credits now, especially since you need four years of those, and only three of math and science.
Not sure about your circumstances, but where we are, while HS requirements cannot be waived or fulfilled with courses taken in earlier grades (I.e., you still need the requisite umber of math courses taken during the nominal HS years), those courses can be included on the HS transcript as elective credits. As in our case, you may need to push up the chain a bit to get clarification on whether this applies in your state.
