Middle school and junior high school cover a period of education that straddles primary education and secondary education and serve as a bridge between them. The terms are used in different ways in different countries.
Taiwanese middle schools (3-year) were originally called junior high school, or chuzhong (初級中學, 初中). However, in August 1968, they were renamed to middle schools, or guozhong (國民中學, 國中) when they become free of charge and compulsory. Private middle school nowdays are still called chuzhong. Taiwanese middle schools are attended normally by those older than twelve. Accompanied with the switch from junior high to middle school was the cancelation of entrance examination needed to enter senior high school.
In the United Kingdom, some English Local Education Authorities introduced Middle Schools to cover Years 4 to 7. However these arrangements have generally been dropped because the standardisation enforced by the English National Curriculum.
In the United States, middle schools generally include grades 6 to 8 while junior high schools include grades 7 to 9.