The short answer is, "It depends."
Here is the long answer:
Although there is no "magic pill" for writing, IEW produces outstanding results; in my experience, it works for every type of student! It just takes a little longer for some kids, and it depends on how much effort you as the Parent Editor are willing to put into it.
I have a son who had some sort of language processing disorder, and he had a very hard time with reading and writing. But through a combination of memorization, reading aloud, and IEW, over time he developed very strong language skills and now he writes with ease. He even writes his own blog posts for his business website.
The Parent Editor must be willing to work with the student to the extent necessary. For some parents that means sitting with the student every day, guiding him and keeping him on task. For other parents, it means a quick review and editing of the paragraphs of an assignment as they are finished.
For students with severe language issues, the best choice might be to start with my PREP-1 class, to prepare the foundation for the writing in Level 1. Please contact me to discuss this option if you would like more information about the benefits of PREP-1.
All students need help and external motivation. The students who do not make progress in my classes are those who do not receive enough oversight. Some of those students are very bright and quick learners, and some are students who struggle.
What makes the difference is how committed the parent is, not how bright the student is.