You have posed a good question which I hope some teachers will respond with resources/websites to give you assistance. We have a group in the Community specifically for special education teachers which may be a good place for you to restate your question and get help from your colleagues. It is an open group so you may join this group Special Education if you wish.
Also you may find help at a website created by the Pennsylvania Department of Education. See http://www.pdesas.org/module/assessment/keystone.aspx. If you scroll to the bottom of the page, you will see some test accommodations for special needs students. I think your question actually asks for help teaching writing. Perhaps this website will give you some ideas: http://www.readingrockets.org/article/215/. I'll be glad to search for more specific references if you want to provide more details.
I hope more Community members will share other websites that may be useful.