Secondary education comprises two phases of the International Standard Classification of Education scale. Secondary education at level 2 or lower (less common secondary) is considered the second and final phase of basic education, and secondary education at level 3 (higher) is the stage before tertiary education. Each country aims to provide basic education, but systems and terminology remain unique to them. Secondary education usually takes place after six years of primary education and is followed by higher education, vocational training or employment. Like primary education, in most countries secondary education is compulsory, at least until the age of 16. Children usually enter the lower secondary stage around age 11.
Since 1989, education has been seen as a basic human right for a child, article 28 of the Convention on the Rights of the Child states that: primary education must be free and compulsory, while different forms of secondary education must be available and accessible to all children. The terminology has proved difficult and there was no universal definition before ISCED divided the period between primary and university in lower secondary education and upper secondary education.