The education system in Japan is as follows:
Elementary School: 6 years – 1st Grade to 6th Grade
Middle School (Junior High School): 3 years – 7th Grade to 9th Grade
High School: 3years – 10th Grade to 12th Grade
College / University: 4 years
In Japan, it is mandatory to go to elementary school and middle school.
But it is very common to go to high school and college / university although it is not mandatory.
After high school, some people choose to go to two-year junior college, or start working. (^-^)