How To Write Letter Late Coming To The Head Office?

The answer to you r question is as follows:
To,
The Headmaster
[school name]

  Dear Sir,
            My child has been late to school because he was feeling sick and I was taking care of him.My child didn't want to miss school so Ibrought him slowly uptil my vehicle and dropped him to school.kindly excuse him.

  Yours Faithfully,
                [your name]