After consulting with her, ask what kind of practice you can do with him to reinforce the skills he is being taught in school. Many children benefit from using the computer to complete writing assignments. Can your child touch type? That's certainly something you could teach him at home that would help him in school with his writing.
If he has difficulty getting his ideas organized and down on the page, there's a software program that might help. You can download the program Inspiration for free for 30 days. There are templates that can help with jumpstarting writing.
The Resource Room website has teaching ideas for writing and other subjects.