This is our first full year homeschooling and I noticed my son really did not have a good handle on grammar. Asking him to write a paper was torture. I had chocked it up to the fact that writing just wasn't his strong point; when, in fact, he didn't understand the parts of speech.
Having a one-page grammar assignment each day is doable for him. It gets right to the heart of things without a lot of fluff. I asked him how he likes it and he said, "I really like this book; I'm starting to really understand."