✔ 最佳答案
(Write down your address at letter top)
(Write down the date of the letter)
To whom it may concern,
My son, (his name, class, student number), has to be absent on (date), from (starting time, put down the hour) to (finishing time). It is because he has to attend the appointment for his leg, which is scheduled on 26/1 at Ming Hoi Hospital.
I hope he has your approval to leave school at the above time. Thank you for your kind attention.
Kind regards,
(Your name and signature)