The first grader is going to write or tell mom how the ear works. The 4th grader is going to do a report on the major causes of deafness in America. The 7th grader is going to do a research paper on the RAS system of the ear, the reticular activity system. She hasn't also been trying to teach an electricity unit and mollusks and shellfish at the same time. All of the units in the other volumes could actually be studied backwards if you wanted.
Some people buy all three books at once and skip from one volume to another.
In fact it is, so she plans to do Honesty out of Volume III next. Many of the decisions in scheduling units, by weeks, months and years is in the Compass. It also has a scope and sequence which is very helpful. Recently someone asked about writing and composition help for mom. You'll have more activities to choose from in Volume I. 5.