K-12 is an expression for the sum of years from elementary to high school i.e. Kindergarten (K) for 4- to 6-year-olds through twelfth grade (12) for 17- to 19-year-olds. This expression is popularly used in the US, Canada, South Korea, Turkey, the Philippines, Egypt, and Australia , to refer to to this levels of education which also free (education in public schools) in these countries.  

This K-12 library contains math concepts associated with these grade levels.