academic institution vs prep school

academic institution

noun
  • An educational institution, dedicated to higher education and research, that grants academic degrees. 

  • An educational institution, dedicated to teaching and/or research. 

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