Here, for the Catholic Home School, are books designed to hone written English communications skills. The Writing Handbook - Second Edition, published by Loyola Press is a fine reference work which the student will want to take with him to college. (It is listed among the required books in the catalogs of several colleges.) Its 908 pages deal thoroughly with grammar, spelling, diagramming, sentence structure, composition, style, agrument and much more.  Gabriel Arquilevich's Fairview's Guide to Composition and Essay Writing and his Writing for 100 Days: A Student-Centered  Approach to Composition and Creative Writing  are sound investments for the home school. Both presume the student already has a good grasp of grammar and sentence structure.