middle school vs senior high school

middle school

noun
  • A school which crosses the traditional divide between primary school and secondary school. 

  • An educational level or stage between primary school and secondary school. 

senior high school

noun
  • An institution which provides secondary education, typically in grades 10, 11, and 12, and often also in grade 9. 

How often have the words middle school and senior high school occurred in a corpus of books? (source: Google Ngram Viewer )