What is the meaning of Secondary_school?

A state school attended between the ages of 11 and 16 or 18 between primary school and university.

The federally designated, graduation-separated classification of grades 9–12 (approximately ages 14–18), regardless of whether they are compiled together in one school or separate from the other grades.

Middle school; junior high school; a school that one attends between the ages of 12-17 (equivalent of grades 7-10 in North America, and years 7-10 in Australia).

Source: wiktionary.org