Easy Grammar series by Wanda Phillips uses the prepositional approach to evaluating sentences. I used Easy Grammar for my children’s grammar lessons during the early to middle years, and I found it to be an effective program. Once a student can identify the prepositional phrases in a sentence, other elements in the sentence are more easily identified. I also appreciated how Wanda Phillips made the sentences in the worksheets straightforward and appropriate for the lesson at hand. The books have been updated since I used the program and now there are books for grades 2 through jr/high.
I wrote about how to plan Easy Grammar, or rather, how I planned it. To read it go to this page at donnayoung.org: Planning Easy Grammar