Organize an end-of-year project, grouping students together. The project should reflect the close of the school year, like writing a short story about what the students have learned that year or working together to clean out cubby holes.
Host an end of the year party for the class. Have snacks and games and encourage students to share what their favorite part of the school year was.
Introduce students to the teachers for the higher grade level, so they will begin to feel comfortable with the new adults.
Organize a lesson plan that outlines the various skills the students will learn the next year, so they're not intimidated by the unknown.
Encourage students to sign one another's yearbooks as a fun way to finish the last day of class.