Does your DC make the same mistakes consistently? For our DD, highly gifted in math, when she could see where she tended to make mistakes on the math it made all the difference. She would work all the way through some moderately hard problem, get to the end and get some basic math fact wrong. Think working a Trig problem, getting to the end and subtracting 3 from 32 and getting 30. Once DD knew she tended to do this, she corrected for it and slowed down on the simpler math at the end. Still made some of the errors, but was much more likely to catch them herself when checking over her answers because she knew that it might be wrong. This was crucial for her when she was taking the SAT because she was 3 years beyond that math and it was really easy to "rush" on the problems.
Also found that talking about test taking strategies like what to study (and how), what will most likely be on the test, how to check problems (many kiddos do not know how to work the problems in reverse because the teacher may not have covered it), as well as assessing what this teacher wants on the test and homework was helpful.
Since your DC's grades were impacted last year, could you give an end of year exam for last year's class and see if she has any weak areas? Shoring those up with a tutor (or knowledgeable parent) may improve things for her now.
