Some A-levels require that the subject is studied at IGCSE level (Maths and Chemistry, for example) but others do not (Business Studies and Psychology). Seek advice and check your facts. At BST we work from the premise that optional subjects at IGCSE are not a requirement for A Level study. Thus, in theory, it should be possible to study History in Years 12 and 13 without having taken it for IGCSE.