Hello! After reading your description, I have chickenpox, and the teacher asked me to write a request for leave. I can write it like this:
A request for leave
Teacher who respects teaching:
I Due to chickenpox, I cannot go to school now. I have asked the teacher for a week's leave. I would like to ask the teacher for permission. I would be very grateful.
Applicant (signature)
Date XX, June 2016