[Your letterhead, if desired; if not, your return address]
[Date of letter—month, day, and year]
[Recipient's first and last names]
[Street or P.O. box address]
[City, State ZIP code]
Dear [recipient's name]:
I am writing to apologize for being late to school on Monday. I know that my arriving late caused some disruption in your teaching the lesson, and I very much regret that. Although this will not fully make up for the inconvenience caused by me being late, I would like to volunteer to help you organize the classroom cabinets sometime soon. If you agree to this, just let me know when we can arrange to complete this project.
In the future, I plan to arrive to school on time, or even early, and will do my best to fully contribute to the smooth functioning of the classroom. Thanks so much for accepting my apology.
[Sender's first and last names]