There are usually two papers in GCSE maths; a non-calculator paper and a calculator paper. Sometimes you may get more. For instance, the AQA 4360 spec has 3 papers and the OCR modular spec has more than 3 papers. For the sake of convenience, let’s assume you only have 2 papers. You may ask, “When do I stop revising for both papers and only concentrate on paper 1 as this is coming up first?”
Well, the general rule of thumb I use is the space between the first and second papers. Suppose the first paper is on a Wednesday and your second paper is on a Friday. The space between the two exams is simply 2 days. That means you should give yourself 2 clear days to revise for paper 1. On Monday of that particular week, you would stop any revision for paper 2 and concentrate solely on paper 1. You will continue to revise for paper 1 until your paper 1 exam is over. Then immediately after, you revise for paper 2. Revision before Monday is split evenly across both papers.
After the exams have took place, you’ll notice that the same amount of revision was dedicated to both papers. That’s the aim here because you want to maximise your result in both exams. Remember this is a general rule of thumb. You can approach each paper however way you like, just make sure that the same amount of time (approximately) is spent on each one.
For a more detailed analysis of approaching multiple exams in one go, see my GCSE Maths In Four Weeks Program.