Write application to principal requesting him/her to grant you a leave as you have stomach infection.
The Principal
UPS School
New Delhi
20 August 20XX
Subject: Request for granting leave
Dear Sir
This is to inform you that I was unable to addend the school on 18 August and 19 August 20XX, since I had a stomach infection. I would be grateful to you if you kindly grant me sick leave for the two days.
Yours faithfully
Riya Sharma
Class VIII
Roll No. 67