Welcome, there are lots of great people on here and lots of ideas!
Writing is a weak area for my DS6 as well. Has nothing to do with academics, it's just that his motor skills are 6, regardless of what level his brain is working at. As a concession to this he types anything over a paragraph long.
He is also all over the map in his levels in various subjects. We work in time frames. He gets 30-45 minutes on any given subject and we work at whatever level he's at. He uses free time to dig deeper into subjects that he loves. His latest fascination is with chemistry and although "class time" is 45 minutes 3x a week, he spends a lot of time on his own working through stuff.
In the beginning I thought like you, that he needed to work on his weak areas, but it just frustrated both of us. The stuff that was weak was mostly from lack of exposure and he's made great strides in those areas now that he has the material. We also do what is referred to as going wide, which means that he does several subjects that wouldn't be on a standard curriculum. Foriegn language, greek and roman mythology, computer programming all in an attempt to slow him down. The important thing is to do wht works for you and your kiddo. There isn't any one right way to homeschool. Enjoy the ride!
