Title: Whole series is a bit off.
Review: As a former teacher and current homeschooler, I find that much of the material in the early levels of this series are not appropriate for the grade levels indicated. I use the books as references but not usually at the grade indicated by the title of the book. The history sections are especially inappropriate. Children at these early grade levels do not have enough background knowledge (i.e., comprehension of the passage of time and the geography of the earth in relation to their own place in it) to fully understand the material presented. Thus, they are very unlikely to retain the knowledge or to apply it meaningfully to other areas of study. Parents trying to stick to these grade levels are bound to be frustrated.
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