I have helped run the exams at our local state school for the last few years. All the exam boards do work together to create the timetable, however, inevitably their are clashes, due to the number of exams taken, students taking weird and wonderful combinations and schools choosing different exam boards. The actual timescale for the exam period in the summer, for example, is extremely short - 6 weeks, with the majority being taken in less than 4 weeks. Every year we have students who have a number of clashes (usually 3 exams but has been 4) and have to accommodate the needs of the student and the requirements of the exam board. I have posted a link to JCQ board - but they are all much of a muchness - for AS and A levels it is 3 exams and 6 hours in one day (ie over that then a deferment can take place) but for GCSE it is 5.5 hours. Obviously, with the 5.5 hours or 6 hours, we have to schedule breaks for meals and rest between the exams but this has to be balanced with the need to get the exams done on that day and posted back to the exam board.http://www.jcq.org.uk/faqs/instructions ... aminations
The overnight supervision thing is not an urban myth! It happens - rarely, but it does. Certainly even in the above situations, students are not allowed to speak to anyone, they have to be escorted on rest breaks and comfort breaks (I've even escorted a student off site for a fag break...!!) and their phones are confiscated for the duration.