A GCSE is a school exam in England and Wales (and in a similar way in Northern Ireland), usually taken at fifteen or sixteen, across a spread of subjects — maths, English, sciences, and others the student has chosen. Most people take a bundle of them, not just one. GCSEs replaced GCE O-levels in 1988. In England the grades are now numbers from 9 (highest) down to 1; older certificates and some other parts of the UK still show letter grades. It is the big checkpoint before A-levels or leaving that academic path. Scotland uses a different system, so “GCSE” is not the word for the whole of Britain. In Taiwan, international schools more often sit IGCSE, a close cousin with a different board and papers, not the same exam. People say each letter: G-C-S-E.