A factor to consider, if your son is anything like mine: ADHD and writing LDs create massive barriers to getting work done. I speak from deep experience when I say that the more challenging and motivating the work, the easier it is for someone like my DS to engage and persevere through the daily battle of dealing with those barriers.
We've had many a fight with school administrators about this ("if he's struggling he shouldn't be in the gifted program"), but his teachers have all consistently agreed that he does better when the work is harder, and falls apart when it is not challenging or engaging enough. Nothing sends his attention in hyperspace faster than make-work on an un-engaging topic doing a task that makes big demands on his writing LDs. It's hard, and it hurts. He needs something that will help him keep going anyways.
