Respected sir/madam,
With all due respect, my name is ______(name) and I am a student of your institution having registration ID ______ (ID number).
Through this email, I would like to mention that I have been preparing for my _________ (entrance exam/ course exam/ any other). In this regard, I hereby request you to kindly grant me __________ (days/weeks) leave so that I can prepare well for my upcoming exams.
Kindly, approve my request and I assure you that I will cover my attendance accordingly. If you have any questions or concerns regarding this matter, please feel free to contact me at any time.
Yours sincerely,
_________ (Name),
_________ (Contact details)