learned society vs prep school

learned society

noun
  • An organization that exists to promote an academic discipline or group of disciplines. 

prep school

noun
  • A private or public school intended to prepare its students to get into prestigious universities. 

  • A private primary school which prepares its pupils for the common entrance examination most commonly at the age of thirteen, and subsequent entry into public school. 

How often have the words learned society and prep school occurred in a corpus of books? (source: Google Ngram Viewer )