Leave application for urgent piece of work

The Principal,
Govt. High School,
City A. B. C.
Most respectfully I beg to say that my father has invited some of his friends to lunch today. He has asked me not to go to school, so that I might be helpful to him in any way he likes. Kindly grant me leave for today only. I shall be very thankful to you for that.
Yours obediently,
Name X. Y. Z.