BJU English is an excellent curriculum. It covers both grammar and writing which includes all of the parts of speech, sentence structure, and development. Grade 6 follows the same set up as grade 2,3,4 and 5, all of which I have used.
This is a great curriculum for grammar and writing. It is very complete, and the teacher's manual provides step-by-step instructions. The lessons are broken up so that every other week is either grammar or writing. So far, I feel my child is getting a better understanding of our English language and her writing is improving.