My suggestion is to take one the first semester and work on it for two "class periods" at home and finish in a semester and then start the next class (if that is possible). My son is doing this in his 9th grade year because his school is on a 4x4 block schedule.
My younger son will probably homeschool and virtual school when he gets to middle school I see him doing this with a lot of classes-finishing in a semester and starting a new class...he works and learns so dang fast that he might not need to double the time expended.
