When I investigated California's Common Core middle school math standards, I found that most of Grade 8 was a review of Grade 7 with a couple of bits added on. It should not require a 'breakneck pace' to cover it all - not by the standards of this board, anyway, and especially not if he's learned half of it already.

Possibly the 7/8 course has more of a spiral path through the material, while Algebra really requires mastery of each concept before moving on? The teacher might assume this makes Algebra more difficult.