The main difference between the GCSE and O-level examinations is in their grading system. The GCSEs utilized an A* to G grading system while the O-levels were graded using the letter-grade system. GCSEs can also sometimes be divided into two different tiers: a foundation and a higher level. Another difference between the GCSE and the O-levels is that the GCSE is offered to schools by various private exam boards.
GCSE exams are more modular in nature and allow for re-takes and supporting coursework. The O-level exam program, on the other hand, was limited in both the scope of subjects it offered and was applied by a single examination board at the national level.
While the O-level examinations were also divided into both ordinary and advanced courses, the tests were not made available to a significant portion of secondary modern pupils. The CSE examination system, which later became the GCSE, was introduced to allow pupils who left school without formal qualifications to earn letters in academic subjects.
Unlike the O-level examinations, the GCSE was initially devised to provide an examination which gives pupils a choice in the type of abilities and subjects on which they can be tested. GCSE examinations cover both academic and vocational subjects.