We added SLP once I was able to argue that DD's speech was impacting her writing because she was sounding out words and spelling them the way she pronounced them. For example 'bright' would be 'bwite'. Not sure if that's what you're dealing with though.
At this point we also have OT, a para to scribe, accommodations allowing oral responses as needed and limits on the amount of written work she is required to do. Our situation is more complicated than 'just' Disorder of Written Expression but that is one of the many things DD has been labeled with.
