“They have learned nothing, and forgotten nothing.”
and variations
Recognized since the 19th century as a borrowing, possibly used by Talleyrand, from a 1796 letter to Mallet du Pan by French naval officer Charles Louis Etienne, Chevalier de Panat: Personne n'est corrigé; personne n'a su ni rien oublier ni rien apprendre. "Nobody has been corrected; no one has known to forget, nor yet to learn anything."
Sources: Craufurd Tate Ramage Ll.D.Beautiful thoughts from French and Italian authors, E. Howell (1866)
Misattributed