It is surprising to see her getting a B, in all honesty, but my concerns are 1. I don't want her to get into the habit of rushing through and passing anyway, then think it's fine; and 2. I'd like her to get into the habit now of working carefully, hopefully down the road it's a skill she's going to need.
I think part of the problem is that in the past she's always been able to coast, not have to study, etc, even with accelerated work. I mentioned above that she does homebound (due to another medical condition), she basically does 5 hrs of school a week, and is done. She might do another hrs worth of homework - a week, not a night. She pulled a 4.0 last year on this schedule, and is headed the same way this year (not counting the math, obviously). We have started doing some supplemental stuff, which helps, but even with the acceleration, she's coasting for the most part.
