You know... now that you've said it's Saxon, that might be one of the reasons. From everything I've heard, (not personal experience) Saxon is particularly difficult to accelerate without a substantial amount of work on the teacher's part. It might not be as simple as testing out of a unit, because each assignment in that unit is meant to be a little bit of a new material and a wide assortment of review problems... It's hard to say what can be skipped, since a large part of any work is meant to go with previous work... so unless he tested out of a whole year I'm not sure it would be that simple to say if a unit was necessary or not -- it may include review that the teacher isn't sure he can go without. In fact the only way I've ever known people to accelerate Saxon is to do as you already are doing and skip the B side.
So anyway, all that to say it might not be attitude on the teacher's part as much as a curriculum that isn't as easy to skip around as you would think.
