The book contains a helpful guide to frequently encountered ed phrases and slogans that roll off the tongue with ease but collapse upon further examination. Most of these phrases and slogans harbor the anti-knowledge Thoughtworld of progressive/constructivist educationists.
This site has helpfully assembled this guide to edspeak.
Here is Hirsch's analysis of one favorite educationist slogan:
facts are soon outdated
Phrased in various ways, this is one of the most frequently stated anti-fact propositions of the American educational community. From being so often repeated, it has achieved axiomatic status. Its ultimate originator may not have been William Heard Kilpatrick, but in the 1920s he was certainly the doctrine’s chief promulgator and popularizer. He taught and spellbound some thirty-five thousand potential professors of education during his brilliant teaching career at Teachers College, Columbia University. He made it a central theme of his book Education for a Changing Civilization (1926). The facts-are-always-changing idea gains what modest plausibility it has from the observation that history and technology are indeed constantly changing. But the truism would seem to be a good argument for teaching the central facts (for instance, the elements of the periodic table), which do not change rapidly, if at all, and which are useful for understanding and coping with the changes that do occur. Facts that quickly lose their educative utility should indeed be cast out of the curriculum in favor of those having a longer shelf life. But a careful case has not yet been made for the transitoriness of significant factual knowledge. Facts are central to “higher-order skills,” and therefore need to be strongly emphasized even (or especially) when the goal of education is seen to be the development of “understanding” and of “thinking skills.”
It would make for a real good discussion to determine what bodies of academic knowledge are supposedly so quickly outdated. I believe Newton's laws and the periodic table will be around for quite a while, to pick just two items.