I am writing this email to inform you that my name is _________ (name) and I am a student of (class/course) having registration number __________ (registration number).
Through this email, I would like to draw your attention that I will not be able to attend the __________ (subject name) exam on __/___/______(date) due to _____________ (mention reason – illness/fever/cold/demise in family/other).
Therefore, I request you to kindly grant me the leave for the above-mentioned date. I promise you that I will give the re-exam as per policy. I hope you will understand my situation and approve my request for the same.
Thank you for your understanding and cooperation. I shall be highly obliged.
___________ (Contact details)