As much as educators claim grammar is only important for communication purposes (and not as an end in itself), relatively few curriculum options relate grammar and composition, instead treating them as two separate disciplines to be studied at different times and in different ways. Not so CLP's Applications of Grammar, a six-volume series introducing high school students to grammar and writing skills simultaneously.
Like most of the curriculum options from Christian Liberty Press, this one is workbook-based and largely student-directed (and very reasonably priced!). Each of the six volumes is accompanied by a teacher's manual that is mostly just an answer key to the worktext exercises, though there are some notes for teachers to present at appropriate moments. This is a middle and high school program, with Book 1 intended for 7th grade and Book 6 for 12th grade (each book covers a single school year).
Most reviewers make a distinction between Books 1-4, and Books 5-6; while the style of the books does change a lot between the fourth and fifth volumes, content-wise there seem to be three stages to the curriculum. Books 1 and 2 are primarily grammar and vocabulary focused; Books 3 and 4 focus on composition; and Books 5 and 6 include review of the whole spectrum of language arts. Books 1-4 are currently in their 2nd edition, reportedly a vast improvement on the first edition.
Each of the first four books contain 10-12 units, with all the lessons in each unit relating to a specific topic (anything from the eight parts of speech, to sentence diagramming, to writing a short story. While Books 1-2 mostly deal with grammar, and Books 3-4 are more composition-oriented, all four books mingle grammar and composition deftly, ensuring kids know why the rules of language exist and how to use them properly.
All lessons include text to read, examples, and exercises. Eventually, students write a research paper, but even in that unit they're doing lots of exercises right up to the moment they're expected to produce a first draft. The books are sparsely illustrated with black and white clip art; otherwise, just black and white text and exercises.
The first four volumes of the program are explicitly Christian in approach. An introduction to each one puts language study in the context of the Christian faith and life, and text and exercises throughout draw on passages of Scripture and elements of Christian doctrine. The publishers are Reformed, but this doctrinal bias in no way makes itself apparent, except for occasional references to the first question of the Westminster Shorter Catechism (Q.: What is the chief end of man? A.: The chief end of man is to glorify God and enjoy Him forever).
Books 5 and 6 depart from the format and content of the first four books in just about every conceivable way. The books (despite a handful of Bible verses in the exercises) are no longer explicitly Christian, and instead of introducing new material the lessons (which are no longer divided into units) are simply review-oriented. Students are reminded about the essentials of punctuation, vocabulary, spelling, composition, etc.
As mentioned above, this is a student-directed course, though obviously parents/teachers will have to correct exercises and grade written work. Also, being available to help students when they need assistance is pretty crucial when kids are learning something as important as how to write a good sentence or paragraph, and how to organize their thoughts for an essay.
It is suggested that students have a fairly strong background in grammar before beginning the program. While this will certainly help, a lot of the material in Book 1 will be repetitive for students who have had plenty of grammar experience, so you might consider starting advanced students at Book 2 (Book 3 would be too late, as the integration of grammar and composition begins in earnest in Book 2).
The first four books in this series are excellent. The authors don't follow a specific compositional approach (Classical, Charlotte Mason, etc.), but they have a good grasp on its purpose and how to achieve clarity, with special emphasis on logical thinking as a prerequisite to good wirting. The grammar and composition integration (at least to the extent exhibited in Applications of Grammar) is rare, and welcome.
Books 5-6 are the weak link. We would recommend completing the first four volumes before moving to another, more rigorous composition-only program, like Put That in Writing or WriteShop. Also, you might be tempted to try to use these books with younger students, but the nature of the progression makes it particularly suited to the suggested grade levels, and younger kids might get lost.
Overall, Applications of Grammar is a good source for grammar and composition instruction. Other programs that take the same approach (notably BJU Writing & Grammar and A Beka Grammar & Writing) are often overwhelming, and filled with unnecessary or too-repetitive exercises. This one steers a more moderate course, giving kids what they need without demanding too much either of them or their parents and instructors.