School of Hard Knocks Is an idiomatic phrase meaning the life itself, and knowledge (and wisdom) gained by working for it. They are not necessarily from a book. It is most-typically used by a person to claim a level of wisdom imparted by life experience, which should be considered at least equal to academic knowledge. "For example, you can learn more common sense from the school of hard knocks, than from most any high school, college or university." Cities: tradesman , "School of Hard Knocks" Urban Dictionary. Last modified June 15, 2014. http://www.urbandictionary.com/author.php?author=tradesman The practical experience life, including hardship and disappointments. For example, A self-made man, he has not attended to college but comes up through the school of hard knocks. This idiom uses knock, as the metaphor for a setback. It was writing in the mid-1800. Cities: The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003,