When I went to school, we had grades 1-5 at one school (ages 6-10) 6th grade at another, 7th grade at another, 8-9th grade at a 'middle school 'sometimes called “junior high” and grades 10-12 at the high school, compulsory schooling ending at age 17 or 18 unless you failed a year, they didn’t allow skipping grades.
When my kids went, there were elementary schools for grades Kindergarten-5 (so ages 5-6 to 10-11) OR K-8, middle school for grades 6-8 if you weren’t at a K-8 and high school for grades 9-12.
US, Florida
When I went to school, we had grades 1-5 at one school (ages 6-10) 6th grade at another, 7th grade at another, 8-9th grade at a 'middle school 'sometimes called “junior high” and grades 10-12 at the high school, compulsory schooling ending at age 17 or 18 unless you failed a year, they didn’t allow skipping grades.
When my kids went, there were elementary schools for grades Kindergarten-5 (so ages 5-6 to 10-11) OR K-8, middle school for grades 6-8 if you weren’t at a K-8 and high school for grades 9-12.