Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, may Allah reward you abundantly for your interest in knowing the teachings of your religion, Islam! We implore Allah to guide all Muslims to the best and to grant them power to overcome their weakness and fulfill their duties to Allah.
In his response to the question you raised, Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee, states:
"Concerning the legal excuses that allow one not to observe the fast of Ramadan, Allah, Exalted be He, says: “And whoever of you is sick or on a journey, (let him fast the same) number of other days; He desireth not hardship for you.” (Al-Baqarah: 185) Sickness (referred to in this verse) that is considered a legal excuse for not observing the fast of Ramadan is that which occurs, becomes urgent, or is aggravated, as a result of fasting.
The same ruling applies to one whose work requires hard labor, so that he cannot observe fast during his work hours, and, at the same time, he has no other means to earn his living. For instance, a baker works in the daytime where it is so hot that fasting becomes unbearable.
However, one must bear in mind that legal excuses - such as illness and hard labor - must be actually found, and not just imagined or expected.
As for students, they are not obliged to study during the daytime; they can strike a balance between their assignments and the available time. So, when Ramadan is in summer, when days are long and hot, students may study their lessons at night and they are not allowed to break the fast-days of Ramadan for the sole reason that they prefer studying during the daytime. Anyway, not observing the fast of Ramadan is by no means permissible, unless fasting entails serious problems, whether physically or mentally. When there is no such excuse, one must not even consider refraining from fasting in Ramadan.
Students may be allowed to break the fast-days of Ramadan if their examination is held during the daytime when it is very hot, i.e. between noon and sunset, in case hunger and thirst affect their concentration.
But, beware, all this applies only to a student who actually feels tiredness while taking his examination, but so long as he does not feel actual tiredness, he is never allowed to break the fast-days of Ramadan. In other words, a student must have the intention to fast, and thus must prepare himself for fasting by taking his pre-dawn meal (suhur). But it is by no means permissible to intend not to observe fasting in order to be able to pass the exam. This is because it is not certain whether fasting will affect a student’s concentration during the exam or not. So is the case when the exam is held early in the morning, when air is fresh and one does not usually feel hunger or thirst, or when it is held in winter or spring. In such cases, a student is not allowed to ignore the fast of Ramadan. Thus, a student who has an examination in Ramadan must have the intention to fast and should take his pre-dawn meal in preparation for fasting during the exam, unless he feels extreme tiredness.
I therefore advise students who are sitting for/have exams during Ramadan to be pious and conscious of Allah, as the honorable verse goes, "And whosoever keepeth his duty to Allah, He maketh his course easy for him." (At-Talaq: 4)"
