Caffeine and exams

A small amount of caffeine, such as the caffeine in one cup of coffee or tea, seems to help many people to 'perform' better than having no caffeine. If people usually have a cup of tea or coffee to start the day, they do not manage so well if they miss that drink.
Large amounts of caffeine may make a person feel more awake, or stop them falling asleep, but they cannot study well or do exams better. In fact the anxious feelings due to the caffeine may make them do worse than usual.