The General Certificate of Education or GCE was introduced in the United Kingdom in 1948. It was intended to cater for the increased range of subjects available to pupils since the raising of the school leaving age from 14 to 15 in 1947. The examinations were graded into ordinary (O) level for 16-year-olds, and advanced (A) level for 18-year-olds.

In 1988, O-level qualifications were replaced by a new system, the General Certificate of Secondary Education, or GCSE. However GCE is still used in some countries like Singapore and some parts of Britain continued to use O levels for some time after 1988.

In 1989 an intermediate level, Advanced Supplementary (AS), was introduced for 18-year-olds who had studied a broader mix of subjects in less depth. The system was revised in 2000 so that all A-level students must now sit AS-levels first.

Increasingly in Singapore, students who perform well in school are given the option to bypass the O-levels, and take the A-levels instead at the age of 18. This scheme is dubbed the "through-train programme".

See also: A-level