The publisher Abeka, revises a grade of their textbooks each year. Often these revisions are very minor and don't affect the quality of the text. These minor revisions on their part make it difficult for us at VHR to rewrite our programs. To do this would mean rewriting all of the schedules, tests, and quizzes for that particular grade. So we have decided to keep our program the same and just use the unrevised editions. Most often this means that you can purchase the texts for a lower price on Amazon or ebay. This also means that you can hand down the books from one child to the next without them becoming outdated.