The General Certificate of Education (GCE) Advanced Level, or A Level, is a main school leaving qualification in England, Wales, Northern Ireland, the Channel Islands and the Isle of Man. It is available as an alternative qualification in other countries.
Students generally study for levels over a two-year period. For much of their history, A levels have been examined by "terminal" examinations taken at the end of these two years. A more modular approach to examination became common in many subjects starting in the late 1980s, and standard for September 2000 and later cohorts, with students taking their subjects to the half-credit "AS" level after one year and proceeding to full A level the next year (sometimes in fewer subjects). In 2015, Ofqual decided to change back to a terminal approach where students sit all examinations at the end of the second year. AS is still offered, but as a separate qualification; AS grades no longer count towards a subsequent A level.

Most students study two or three A level subjects simultaneously during the two post-16 years (ages 16–18) in a secondary school, in a sixth form college, in a further and higher education college, or in a tertiary college, as part of their further education.

A Levels are recognised by many universities as the standard for assessing the suitability of applicants for admission in England, Wales, and Northern Ireland, and many such universities partly base their admissions offers on a student's predicted A level grades, with the majority of these offers conditional on achieving a minimum set of final grades.

History
A Levels were introduced in 1951 as a standardised school-leaving qualification, replacing the Higher School Certificate. The examinations were taken on a subject-by-subject basis, the subjects being chosen according to the strengths and interests of the student. This encouraged specialization and in-depth study of three to four subjects. At first, A Levels were graded as simply distinction, pass or fail (although students were given an indication of their marks, to the nearest 5%). Candidates obtaining a distinction originally had the option to sit a Scholarship Level paper on the same material, to attempt to win one of 400 national scholarships. The Scholarship Level was renamed the S-Level in 1963.
Quite soon, rising numbers of students taking the A-level examinations required more differentiation of achievement below the S-Level standard. Grades were therefore introduced, with recommendations by the Secondary School Examinations Council (SSEC) of approximate proportions of pupils for each grade.
The O grade was equivalent to a GCE Ordinary Level pass which indicated a performance equivalent to the lowest pass grade at Ordinary Level.
Over time, the validity of this system was questioned because, rather than reflecting a standard, norm referencing simply maintained a specific proportion of candidates at each grade, which in small cohorts was subject to statistical fluctuations in standards. In 1984, the government's Secondary Examinations Council decided to replace the norm referencing with criterion referencing: grades would in future be awarded on examiner judgement thus eliminating a possible inadequacy of the existing scheme.
The criterion referencing scheme came into effect for the summer 1987 exams as the system set examiners specific criteria for the awarding of B and E grades to candidates, and then divided out the other grades according to fixed percentages. Rather than awarding an Ordinary Level for the lowest pass, a new "N" (for Nearly passed) was introduced. Criticisms of A level grading continued, and when Curriculum 2000 was introduced, the decision was made to have specific criteria for each grade, and the 'N' grade was abolished.
In 1989, Advanced Supplementary (AS) awards were introduced; they were intended to broaden the subjects a pupil studied post 16, and were to complement rather than be part of a pupil's A-level studies. AS-Levels were generally taken over two years, and in a subject the pupil was not studying at A-Level. Each AS level contained half the content of an A-Level, and at the same level of difficulty.
Initially, a student might study three subjects at A-Level and one at AS-Level, or often even four subjects at A-Level. However, due to decreasing public spending on education over time, a growing number of schools and sixth form colleges would now arrange for their pupils to study for three A-Levels instead of four.





