or first stage of basic education Level 2 – Lower secondary or second stage of basic education Level 3 – (Upper) secondary education Level 4 – Post-secondary non-tertiary education Level 5 – First stage of tertiary education Level 6 – Second stage of tertiary education Within this system, Levels 1 and 2 – that is, primary education and lower secondary – together form basic education. Beyond that, national governments may attach the label of secondary education to Levels 2 through 4 together, Levels 2 and 3 together, or Level 2 alone. These level definitions were put together for statistical purposes, and to allow the gathering of comparative data nationally and internationally. They were approved by the UNESCO General Conference at its 29th session in November 1997. Though they may be dated, they do provide a universal set of definitions and remain unchanged in the 2011 update. The start of lower secondary education is characterised by the transition from the single-class-teacher, who delivers all content to a cohort of pupils, to one where content is delivered by a series of subject specialists. Its educational aim is to complete provision of basic education (thereby completing the delivery of basic skills) and to lay the foundations for lifelong learning. Lower secondary education is likely to show these criteria: entry after some 6 years of primary education the requirement for more highly qualified teachers teaching only within their specialism exit to Level 3 courses, or vocational education, or employment after 9 or more total years of education. The end of lower secondary education often coincides with the end of compulsory education in countries where that exists. (Upper) secondary education starts on the completion of basic education, which also is defined as completion of lower secondary education. The educational focus is varied according to the student's interests and future direction. Education at this level is usually voluntary. (Upper) secondary education is likely to show these criteria: entry after some 9 years of basic education typical age at entry is between 14 and 16 years all teachers have level 5 qualifications in the subject they are teaching exit to Level 4 or 5 courses or to direct employment. More subjects may be dropped, and increased specialism occurs. Completion of (upper) secondary education provides the entry requirements to Level 5 tertiary education, the entry requirements to technical or vocational education (Level 4, non tertiary course), or direct