These ebooks are found at the learning express ebooks website. You can use these free online ebooks to teach your homeschoolers. You can also purchase the book versions and probably more up to date versions of these books at amazon.com.
Here are some of the titles you should check out.
501 Grammar and Writing Questions
501 Sentence Completion Questions
411 SAT Writing Questions & Essay Prompts
501 Writing Prompts
Grammar Success in 20 Minutes a Day
How to Write Great Essays
Research & Writing Skills Success in 20 Minutes a Day
Writing Skills Success in 20 Minutes a Day 4th edition
Goof-Proof College Admissions Essays
SAT Writing Essentials
Write Better Essays in Just 20 Minutes a Day, 2nd Edition