Your school don't choose when you take your GCSE exams - the exam boards do. All schools in the country take a given GCSE exam at the same time on the same day (to reduce cheating). So if you know what subjects you're taking, and you know what exam board each subject is with (they won't all be the same) then you can just look at the timetable published by each of those exam boards. I've provided the link to AQA May/June 2024 timetable above.
If you want to wait for your school to go through those timetables and match your subjects and your exam boards to them, to generate a personalised timetable, then that's fine too. However, that's not likely to happen for several months.