Introduce the subject of the post office by reading to the class. "The Jolly Postman" by Janet and Allan Ahlberg is suitable for very young children and is a fun story that will prompt discussion of mail and letters. "The Post Office Book: Mail and How It Moves" by Gail Gibbons is a nonfiction book that offers a step-by-step guide to the journey a letter takes once it is mailed. In between and after the books, allow class discussion. Most children will already have visited the post office and have an anecdote to share. Discussion is also the time to determine the children's understanding of how mail moves.
Discuss with the class the reasons people write letters, making sure to discuss not only social letters such as party invitations, but also business mail such as bills. Also discuss the conventional layout of a letter and the recipient's address. Finally, talk about the importance of the stamp. Have the children write a letter to a person of their choice, following the correct layout. Help the class to fold their letters and to seal them in an envelope before addressing it. Use stamp-shaped stickers and ensure that each child's letter has one. Allow each child to "mail" their letter in a mailbox prepared in advance.
An educational visit will consolidate children's knowledge and understanding and allow them to ask any questions to real postal workers. If it is possible, arrange a guided visit of a large post office and sorting office. Ask postal workers to guide the children through the building in a way that allows them to follow the "journey" that a letter would take. Postal workers should explain how letters are sorted, using ZIP codes, states, cities and streets.
Enrich the children's understanding of the post office system by setting up a school post office. Use arts-and-crafts time to make a few mailboxes to place around the school and speak with other teachers, asking that they spend a short amount of class time asking the students to write letters to friends or teachers in different classes, which they can then mail in the mailboxes. Ensure that each child in the class has a job. There will be mail carriers who collect the mail that has been sent and bring it back to be sorted, children who sort the mail into sacks for each classroom and children who deliver the mail to the recipients.