There are two prime reasons for Exam Fever. If he does so, he is sure to collapse even before a bullet hits him. Likewise, before children face exams, it must be made sure that they are prepared well in advance. Children could be well prepared and yet perform badly. This is only because of pressure.
Children face pressure from their peer group or siblings in the form of competition.
It is implied that winning is the only 'right' way to perform. Don't persistently push them to study and order them to sacrifice their play time. Prepare a suitable time table and be open to changes. Encourage children to exercise for at least half an hour either in the morning or in the evening. This will relax them and help them perform better in their studies.