This is the teacher's supplement for the three books in the God's Design for Chemistry/Ecosystems study. Since the books in this series were rewritten, there are a number of differences. There didn't use to be a teacher's book, since all of the information was included right in the textbooks. Now, however, the setup is a little different. -The tests, quizzes, and activity sheets have been removed from the text book, as well as the answer key, master lists, etc. -These tests/quizzes/activities are now sold in a seperate "glue pad" (with tear off sheets) (Retails for $7.99; our price $6.39). There is 1 glue pad per 3-book set (the glue pad would have all of the activities and tests for the entire "Chemistry" 3-book series). -More lab activities have been added to the text book per unit. -There is now a seperate teacher's book (retails for $29.99, our price is $23.99) that contains a CD copy of the glue pad worksheets. It contains additional helps (a la Answers in Genesis style), as well as the answer key and master supply list. Like the glue pad, there would be 1 teacher book per 3-book series. You don't need the glue pad if you have the CD copy that comes with the teacher's book. Based on the thoroughness of the student book, it doesn't look to me as if the answer key would be entirely necessary. The student books would stand alone. The glue pad is convenient mainly for the tests if you want to award your kids a grade point average or to reinforce vocabulary (through word-search puzzles, etc.). I've also seen references throughout the text to the activity sheets on the glue pad (like: "Now do the Word Search puzzle...."). All in all, though the teacher's supplement isn't entirely necessary, there is no doubt that it is economical (one teacher book, including the glue-pad cd, for all three textbooks) and does enhance the program. For additional savings, see the link below for our amazing deal on the purchase of the God's Design for Chemistry set. Pictured is "God's design for Ecosystems" - one of the 3 books featured in this teacher's guide.