In a letter to Rupert Hart-Davies on 29 November 1956 George Lyttelton included this statement from William Johnson Cory (1823-1892, Master of Eton 1845-1872) on education:

At school you are engaged not so much in acquiring knowledge as making mental efforts under criticism. A certain amount of knowledge, you can indeed with average faculties acquire so as to retain; nor need you regret the hours you spent on much that is forgotten, for the shadow of lost knowledge at least protects you from many illusions.  But you go to a great school not so much for knowledge as for arts and habits; for the habit of attention, for the art of expression, for the art of assuming at a moment’s notice a new intellectual position, for the art of entering quickly into another person’s thoughts, for the habit of submitting to censure and refutation, for the art of indicating assent or dissent in graduated terms, for the habit of regarding minute points of accuracy, for the art of working out what is possible in a given time, for taste, for discrimination, for mental courage, and for mental soberness.”

Reference:
Rupert Hart-Davis (Editor) [1978-79]: The Lyttelton Hart-Davis Letters:  Correspondence of George Lyttelton and Rupert Hart-Davis, 1955-1962. London: John Murray.