Middle school, also known as intermediate school, junior high school, junior secondary school, or lower secondary school, is an educational stage between primary school and secondary school.

In Afghanistan, middle school includes grades 6, 7, and 8, consisting of students from ages 11 to 14.

In Algeria, a middle school includes 4 grades: 6, 7, 8, and 9, consisting of students from ages 11–15.

The ciclo básico of secondary education (ages 11–14) is roughly equivalent to middle school.

No states of Australia have separate middle schools, as students go directly from primary school (for years K/preparatory–6) to secondary school (years 7–12, usually referred to as high school).

As an alternative to the middle school model, some secondary schools classify their grades as "middle school" (years 5,6,7,8 where primary and secondary campuses share facilities or 7,8,9 in a secondary campus) or "junior high school" (years 7, 8 and 9) and "senior high school" (years 10, 11 and 12). Some have three levels, "junior" (years 7 and 8), "intermediate" (years 9 and 10), and "senior" (years 11 and 12). Some schools run a specialised year 9 program separate from the other secondary year levels.

In 1996 and 1997, a national conference met to develop what became known as the National Middle Schooling Project, which aimed to develop a common Australian view of

The first middle school established in Australia was The Armidale School, in Armidale. Other schools have since followed this trend.