IGCSE
The IGCSE programme (International General Certificate of Secondary Education) prepare international students for A-Level and/or IB.
Students study between 5 and 7 subjects, English, Maths and Science being included. Each school has a list of available subjects for IGCSE students. At the end of Year 11, students take exams in each studied subject and receive IGCSE Certificates.
A level study
In the UK school system, once a student reaches the age of 16, they can start a 2 year programme which leads to A (Advanced) level examinations. Students specialise in 3 or 4 subjects, that are usually relevant to the degree subject they wish to follow at university. A levels are state examinations and are recognised by all UK universities and by institutions worldwide.
At the end of Year 13, following the examinations in each subject, the students receive A level Certificates.
International Baccalaureate (IB)
Those who would like to study more than 3-4 subjects, may continue their studies in a broader number of subjects with the International Baccaularete Diploma Programme, offered by some independent schools.
During the IB, students study 6 subjects, 3 at higher level (HL) and 3 at standard level (SL). Each school offers different subjects at different study levels (HL/SL). The IB programme also includes a compulsory Core programme consisting of Theory of Knowledge (TOK), Extended Essay (EE) and Creativity, Activity, Service (CAS).
Students take written examinations on each subject at the end of their courses
Reference - https://www.brightworldguardianships.com/en/guardianship/british-education-system/