Why I think this is so great is that it is hands-on. Colored clue cards are used to lay out each sentence, "diagramming" parts of speech in a very tangible way. Parts of speech are taught beginning with "articles," "nouns," and "verbs" and moving gradually into advanced English grammar. The teacher explains the part of speech that is being focused on and gives some sentences for the children to practice on, laying their parts of speech cards out in order. After this hands-on workout, the children may do the workbook page that reinforces the lesson in writing. Teacher's edition (included) contains complete, simple instructions for teacher, and workbook answers. I've never seen a program where the kids actually "played" at diagramming sentences, or rather identifying parts of speech and laying out sentences and truly understanding the parts of speech, and grammar. Usually everything is done in workbook format, so this is a really fun breath of fresh air when it comes to grammar programs. You can use the same program throughout the learning years, for all your children.
My children started when they were about 8 or 9 years in our homeschool, and keep going up through high school, using the same cards that come with the Basic Winston Grammar kit. They like it, it is challenging and fun. We make it very interactive, working together on it, laying out the cards for each sentence in the workbook. I set it up with two kids like a game, with them sitting back to back so they can't see each other's cards, and they race to be the first to lay out the sentence. It's fun! The kids really remember their grammar well. I've even learned grammar doing Winston Grammar with my kids, and I was an English major in college for the first couple of years! It is thorough and fun!
Haven't found anything I liked better in 25 years of homeschooling!