military school vs prep school

military school

noun
  • A secondary school (or middle school) that prepares its students for joining the military. 

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 military school and prep school occurred in a corpus of books? (source: Google Ngram Viewer )