What I did for GCSE study leave (but before my exams kicked off) was to stick to my school timetable, since it has a sensible spread of times. But for during exams, I would recommend getting a spreadsheet with the dates and times of your exams marked in, then put a revision slot for that subject right before it: e.g. if you have biology at 13:00, study biology that morning, or look at biology flashcards over lunch if you have another exam that morning. If you have an exam at 9:00, look at your notes on the bus to school and the evening before. Put in revision slots for all the subjects/topics you have in a week in the weekend before. If you have a free day, get ahead on the topics you find most difficult but don't have for a while yet. For optimum learning, keep your sessions to 25 minutes and a 5 minute break, and you can cover 1 topic per 25 minute session.
I hope this is helpful, and good luck with your exams!