Many years ago, I did some tutoring for a friend in elementary education math. It was sorta neat, in that they were teaching them different number theories (in practice some discrete math) and forcing them to learn how to work with numbers in much the same way their first students would. It was smart and made a lot of sense when viewed in this manner.

The problem was the author of the book had no idea why they were doing this, or what the purpose of this was. It provided the curriculum, but had already lost the inherent reason behind it.