Students hear the words "I'm sorry" but rarely see those words. Students, teachers, and everyone else make intentional and unintentional mistakes everyday. The unintentional mistake of dropping a book, requires a simple "I'm sorry" but throwing a book at someone requires a little more.
Writing apology letters is a skill that is best taught in elementary school. Students learn how to write thank you letters but apologies are usually only spoken. An I'm sorry letter allows the student to reflect on why her behavior was not acceptable and it makes her responsible for her actions. Often, the spoken apology is said right after the incident and there is little thought or reflection on their choice behaviour.
A student who reflects can weigh the advantages and disadvantages to his actions. By reflecting, they can make a conscious choice of repeating the action and receiving a consequence or changing their action. An apology letter is an awesome tool to have students stop and think about their actions and problem solve for solutions.