primary school vs senior high school

primary school

noun
  • A formal, obligatory kind of school that typically begins with nursery school or first grade and ends at fifth or sixth grade. 

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 primary school and senior high school occurred in a corpus of books? (source: Google Ngram Viewer )