We're currently using Hake Grammar 5 for 5th grade, and my son and I both like it. We're doing 3-4 lessons per week in order to complete the book in 1 school year. I introduce the lesson to him, then turn him loose to do the exercises independently. There's a good bit of review built in, and so far, his retention seems to be pretty good. We only do the grammar portion and not the optional writing book that is available. http://www.hakepublishing.com/