Ask your students to tell you some rules about crossing the street (such as looking in both directions). Talk about why it is so important to practice safety when crossing streets.
Show your class a picture of a crossing guard and ask them if they know what the person's job is. Discuss how a crossing guard helps people safely cross the street.
Visit a crossing guard at your own school or ask a crossing guard to come speak to your students. Ask the guard to explain to the kids what they should do when they cross the street. Then practice crossing with the help of the guard.
Give your preschoolers coloring printouts of crossing guards and have them color them, or ask students to draw a picture of themselves following the instructions of a crossing guard while crossing the street. Post their work around the room.