The term sixth form describes the school years numbered 12 and 13, which are called the Lower Sixth (L6) and Upper Sixth (U6) by many schools.
The term survives from an earlier system when the first five years of English secondary schooling were known as forms (which would originally have been long backless benches on which rows of pupils sat in the classroom). Pupils started their first year of secondary school in the first form or first year, and this was the academic year in which pupils would normally become 12 years of age. Pupils would move up a form each year before entering the fifth form in the academic year in which they would have their sixteenth birthday. Those who stayed on at school to study for A-levels moved up into the sixth form, which was divided into the Lower Sixth and the Upper Sixth. In some private schools, the term Middle Sixth was used in place of Upper Sixth, with the latter being used for those who stayed on for an extra term to take the entrance examinations that were previously set for candidates to Oxford or Cambridge universities. Other schools described these Oxbridge examination students as being in the Seventh Form or Third Year Sixth.
The system was changed for the 1990–1991 academic year and school years are now numbered consecutively from primary school onwards. Year 1 is the first year of primary school after Reception. The first year of secondary school (the old first form) is now known as Year 7. The Lower Sixth is now Year 12 and the Upper Sixth is Year 13. However, the term "Sixth Form" has still been retained as a vestige of the old system and is used as a collective term for Years 12 and 13. Public (fee-charging) schools, along with some state schools, tend to use the old system of numbering.
In some parts of the country, special sixth form colleges were introduced beginning in a particularly important phase of student life. A large proportion of English secondary schools no longer have an integral sixth form. This is mainly related to reforms in the later 20th century, where different political areas became a factor in the introduction of colleges instead of the original sixth forms. There are now numerous sixth form colleges throughout England and Wales, and in areas without these, sixth form schools and specialist further education (FE) colleges called tertiary colleges may fill the same role.
Sixth form is not compulsory in England and Wales (although from 2013 onwards, people of sixth form age must remain in some form of education or training in England only, the school leaving age remains 16 in Wales); however, university entrance normally requires at least three A2-level qualifications and perhaps one AS-level. Students usually select three or four subjects from the GCSEs they have just taken, for one "AS" year, the AS exams being taken at the end of Lower Sixth. Three subjects are then carried into the A2 year (the dropped AS being "cashed in" as a qualification) and further exams are taken at the end of that year. The marks attained in both sets of exams are converted into UCAS points, which must meet the offer made by the student's chosen university.