You need 5 days' leave in advance. Now, write an email to your headmaster asking for 5 days' leave in advance.

 From       :shiponislam@gmail.com
To              :headmasternpk@gmail.com
Subject    :Regarding 5 days' leave in advance.

Dear Sir,
With due respect and humble submission, I would like to inform you that my elder brother's marriage ceremony is going to be held on 14 January 2023. So, I have to perform various activities on that day.

I, therefore, request you to grant me 5 days' leave in advance with effect, from 12 January 2023.

Obediently yours
Shipon Islam
Class-IX, Roll no-03