To test this theory, I just completed a two month unit on dragons with all of the ELL children that I work with from first to fifth grade. Through a movie, drawings from different cultures, and discussions, the children became completely engaged in the subject. First, they drew their own dragons, then they wrote dragon stories to go with their pictures. In the editing process, they were able to read the stories and correct the grammar in their writing. They were also open to suggestions from me and my assistant to alternative ways of saying that same thing that would be grammatically correct. Because the children had written the stories themselves, the grammatical suggestions were important to them because they wanted their readers to be able to understand what they had written. After making the final written corrections, they orally recorded their stories. Of course, the final products still contained many grammatical errors, but the students had found the errors that they were developmentally ready to process. It is this type of self-correction that can facilitate the learning of English and new grammatical forms.
There is now a very interesting discussion taking place on ELL Advocates about the teaching of grammar in ELL classrooms in Oregon.