school of hard knocks

1870, school + of + hard + knocks (“setbacks”).

school of hard knocks (plural schools of hard knocks)

1. (idiomatic, chiefly US) The source of an education consisting of real-world experiences, especially adverse experiences.
   • 1870, The Men Who Advertise: An Account of Successful Advertisers, New York: Rowell, p 161:

     Trained, however, in the school of hard knocks, he now had learned the theory of success, and from that time on has had it.

   • 2000, Walter A. McDougall, "Who Were We in Vietnam?," New York Times, 26 Apr. (retrieved 3 Aug. 2008):

     Did Vietnam's school of hard knocks teach Americans to do peacemaking and state building right?

• university of life

• experience is the best teacher