These are strictly school-related books that we use.
Core knowledge sequence: Content guidelines for grades K-8 An outline of each subject for each grade. We use this to write up our Individualized Home Instruction Plan each year (required in New York State).
What Your Fourth Grader Needs to Know: Fundamentals of A Good Fourth-Grade Education (The Core Knowledge Series) This book (there's one for each grade) covers in more detail the info outlined in the Core Knowledge Sequence book. We use this to fill any gaps we may have as we progress through the school year.
Saxon Math 5/4: Home School The curriculum we love to hate. It is amazingly comprehensive, and truly not liked by many homeschoolers, but also viewed as the more rigorous.
Language Arts (Spectrum) Typical workbooks covering language arts for this year. We suppliment with Daily Grams or writing out quotes.
Personal Trainer: Math Ok, this isn't a book. This is a Nintendo DS game, but it really is all about math, and it takes only a few minutes a day to help the kids get some math practice in. Plus, I can do it too, so it's a family thing.
