* The exam board: Each exam board (e.g., AQA, Edexcel, OCR) sets its own grade boundaries.
* The subject: Grade boundaries differ between subjects; a 70% in one subject might be an A, while in another it might only be a B or even a C.
* The year: Grade boundaries can shift slightly from year to year depending on the overall performance of students nationally.
To find out the percentage needed for a specific grade in a particular GCSE subject, you need to consult the grade boundaries published by the relevant exam board after the exams are marked. These are usually available on the exam board's website.