It is not permissible for one who is accountable to break his fast in Ramadaan because of exams, because that is not one of the excuses that are allowed in sharee’ah. Rather he has to fast, and do his studying and revision at night if it is too hard for him to do that during the day.
Those who are in charge of exams should be kind to the students and not make the exams in Ramadaan, thus serving two interests, the interests of the fast and to help the students prepare for the exams. It was narrated in a saheeh report from the Messenger of Allaah (peace and blessings of Allaah be upon him): “O Allaah, whoever is put in charge of any of the affairs of my ummah and is kind to them, show kindness towards him, and whoever is put in charge of any of the affairs of my ummah and is harsh towards them, show harshness towards him.” (Narrated by Muslim in his Saheeh). So my advice to those who are in charge of exams is to be kind to the students and not to have exams in Ramadaan, but to have them before or after. We ask Allaah to give us all strength.