Following is a letter written by Kailash to his Class Teacher, requesting leave for going to a temple. You can use the same format by simply replacing the name with yours and adding relevant details in respective places.
The Class Teacher,
My father has planned to go to a temple in Kerala for a family ritual on (Date). Since everyone in our family are supposed to take part in the same I will not be able to come to school on (Date and Date 1).
Kindly accept my request and grant me permission to be away from our class on those 2 days alone.