Exam is important part in student life. The way to stay focused during an exam is to ignore everybody around you, the people writing angrily right from the very beginning, or anything else happening in the examination room.
Remember, it’s your examination and nobody else’s and it’s the examiner that will decide whether you’ve done well enough to pass or not, nobody else. So, make sure your mind is completely separate from everything else that’s going on in the examination room, and if you carry out good training before you go and you’ve prepared yourself in terms of how you move toward the examination room and you’ve read over your paper,
I think you’ll find yourself fairly focused and the time will pass very quickly as well.