Respected Sir/ Madam,
My name is ____________ (name), studying in ________ (class) of your reputed school __________ (school name). My roll number is __________ (roll number).
Through this email, I would like to inform you that I will not be able to attend my classes for __________ (number of days) from __/__/____ (date) till __/__/_____ (date) as I am not feeling well. Respected, I am going through ___________ (fever/ cough/ cold/ sore throat/ any other).
Therefore, I request you to kindly grant me sick leave. I shall be highly obliged for your kind support.
____________ (Roll number)
____________ (Parent’s contact number)