So I'm taking a break, and it dawns on me to share an organizing-a-piece-of-writing technique I learned back in the far-off days when I was habitually employed. I used it with Big Guy, when I was still homeschooling him and he was having a tough time writing a paper on John Wilkes Booth.
The first step is to write each of idea as a pithy newspaper headline. This prompts for to-the-point verbiage. Big Guy came up with "Booth Born a Bastard" and "Mudd Makes a Mistake" and other somewhat eye-popping headers. Then he wrote each headline on a sticky note. He was allowed to put supporting facts as bullets beneath the headline, for later reference. I pointed him to a blank wall, where he could arrange the headlines, and rearrange them, and rearrange them until he had an order that he liked (and made sense).
From there I had him write the first sentence in the 'article' for each of his headlines. So instead of writing "Booth Born a Bastard" he put down something like, "On May 10, 1838, Mary Ann Holmes, mistress to noted Shakespearean actor John Brutus Booth, gave birth to her ninth child." Starting a 'story' from each headline encourages using strong verbs, and makes things tie together. Big Guy ended up with a good paper.
Of course, there's also the high-tech approach to organizing writing. I know a lot of people whose children have had breakthrough experiences using Kidspiration (there's a 30-day free trial). The key thing is to keep ideas from getting log-jammed by organizational challenges.