How to write a letter to explain why a child was absent from school?

Dear <teacher's name>,

Please excuse the absence of <child> from school on <date>. He(she) was sick with <name of illness>.

Thank you,

<your signature>

If it was for some reason other than illness, state the reason.

To whom it may concern,

Please excuse the absence of my daughter Sofhia Nascimento from school last week. She was sick with the flu.

Thank you,

Valdenir Nascimento