To be proficient in grammar, the student must have lots of practice. In Grammar for the Well-Trained Mind, the instructions are the same each year, but the workbooks have different sentences each year for the students to practice on. So, the same instructor text can be used for each of the four workbooks. The Purple and Red Student Books and Answer Keys are available now, the Blue Books will be available Q4 2019; the Yellow books will follow later.
We named the workbooks using colors instead of level numbers to show more clearly that the workbooks are not sequential and do not increase in intensity - they can be used in any order, but that they are different so the student doesn't get bored practicing grammar. This article explains the concept a little further: https://welltrainedmind.com/a/grammar-well-trained-mind-new-titles-great-curriculum/
You can find more information on our Articles page (link follows), where Susan Wise Bauer provides videos explaining the series, gives some teaching tips, and shows a role-play of a teaching situation.
We offer the first six weeks in this sample so you can take a look at the program. Grammar for the Well-Trained Mind Sample
We sell two reference books: The Grammar Guidebook, and The Diagramming Dictionary. These are not required texts, but they give both instructors and students information that is useful throughout their academic careers. You can find them on this page: Well-Trained Mind Grammar Reference Books