My daughter is in second grade in the K12 program, which is a curriculum used by online schools in almost every state. We are enrolled in MNVA.
I would say one in every four units in her "Writing Skills" class (they have separate classes for Literature and Comprehension, Spelling, Vocabulary, Writing Skills, and Handwriting.) is a composition unit. Of course the in between units are grammar, etc (nouns, pronouns, adjectives, verbs, adverbs, etc), but the composition units she's had lately were "Write a friendly letter" and "Compose a paragraph." They go through a MULTIPLE step process in doing these, and the paragraph thing only brought her to the end of her first draft...she has three MORE units on paragraphs spread out through the remaining semester where she will be proofreading, embellishing, rewriting, and publishing, etc. Even last year they had to write a researched report on an animal assigned to them by their "teacher", and I'm sure they'll do something similar this year as well.
I don't know if you mean "Communication Arts and Science" to be one thing or if you're also concerned about his Science curriculum. In science, we have finished complex units on simple machines, force (including measuring force, which even I thought was a bit much at this age), magnetism, the scientific method, the digestive system, and we're getting ready to start a unit on geology.
My biggest concern for public schools is that they don't seem to teach history AT ALL. Again, in second grade history, my daughter has already learned about the rise and fall of Greece and Rome, the Byzantine Empire, and is now working her way through the Dark Ages...and the lessons go into an amazing amount of detail for this age. She loves it. Her stepsister, who is in fifth grade at a private school, has not had a history class yet, while my daughter started history in K.
If you have the time and energy, at least check out the k12 program at www.k12.com ...you can see if your state has a virtual academy, and submit a form to be able to check out examples of their curriculum at the appropriate grade level.
(Oh, and reading...what books are they reading? I didn't cover that, but we have read Peter Pan, Knights of the Round Table, Balto, The Long Way Westward, Sam the Minuteman, etc etc for Literature, as well as an extensive collection of fables and poetry.)