If I had any really brilliant suggestions, I'd be using them, but I think it might just be the age. I was snapping at my own ds8 this morning and feeling like a lousy parent because he had done his math review and made some really silly mistakes. I felt bad because it is 5th grade math and I briefly thought, "is this just too hard?" but then I realized that the mistakes were all STUPID stuff - like having the right answer in the "work" area and copying it incorrectly to the "answer" area, or not including decimals, or adding 2 and 6 to get 12.
I think part of the problem IS the age. Ds10 rarely got perfect scores in 3rd grade, even though if you actually asked him to walk you through a problem, he knew it nearly 100% of the time. Now, in 5th grade, he usually does get perfect scores. We tried lots of different things with him in earlier grades: putting check marks next to each one he double-checked, circling the "question" that was really being asked, underlining the pertinent numbers in a word problem, and double-checking the answer with traditional math when they were asked to use goofy methods like partial sums. But honestly, the biggest solution was time- just waiting until he was able to develop those skills on his own.
Why is it important that your ds get good grades? I think that if it's just to teach him, you can let go a little and give him time. However, if it's important for the school so that they continue to give him enrichment or that he qualifies as gifted or something like that, then you have more of a problem. You might want to meet with the teacher or point out the type of mistakes he makes. I have a friend whose daughter would make silly mistakes no matter what, so she met with the teacher and requested that she be given more challenging work no matter how she performed. For example, if she breezed through the spelling list and made really silly mistakes, she would have her daugher learn both the regular and the accelerated list. If she made arithmetic errors on the pretest in math, she would ask that she still be given some of the advanced homework in addition to the regular stuff (because she knew that her dd knew the stuff, she just didn't think).
If the only issue is really grades, then the bottom line is that they don't matter that much in 3rd grade, so I'd let it go a bit (obviously, easier said than done, since I was the mom snapping about rushed and thoughtless work this morning, lol!). Oh, one other thing that helped was setting times for homework, IF he rushes through. My ds10 gets advanced work, but because his math teacher isn't sure how long it will take the small group of kids doing the alternate homework, she says, "set the timer for 20 minutes." It's actually been great to see him sit and spend the time on it. I am thinking about doing the same thing with ds8 - instead of him racing through his homework in ten minutes and making stupid mistakes, saying, "you need to work for 30 minutes on each of the four nights you have homework. If you race through your own, I'll give you a workbook." That might take away the incentive to finish quickly??
Theresa