The only thing that I *think* would help is getting in the habit of checking an answer to see if it makes sense.
Ahh, but according to my son, he doesn't need to check them because he makes no mistakes! And apparently he doesn't remember what he needs to do in order to "check his work."
Hmmm. Since it's the high school class that is a problem, do you think he's going to encounter more difficulty across the board when he's in high school next year? Or is this something isolated to math and he'll continue to breeze by during HS?
My wife & I discussed this today and figured that he'll have problems with anything computational, like Chemistry & Physics. For everything else, he gets to rely on his processing speed and freakish memory.
Perhaps the workload of AP courses will prove taxing, but probably more related to the volume rather than complexity.