Rhetoric, by Aristotle (selections)
Why Knowledge Matters, by E. D. Hirsch, Jr.* (Selections)
The Schools We Need and Why We Don’t Have Them, by E. D. Hirsch, Jr.
Why Johnny Can’t Read, by Rudolf Flesch
Why Johnny Can’t Add: The Failure of the New Math, by Morris Kline (free online)
How to Read a Book, by Mortimer Adler
Begin Here: The Forgotten Conditions of Teaching and Learning, by Jacques Barzun
If you cannot find a used book on the link listed above, it can still be found by searching the following sites, all of which can search multiple bookstore databases for the book you need:
You may also be able to find the book on Ebay.