Sixth-grade graduations are important days in students' lives because that is often their last day in the elementary school system. After the sixth grade, the student will go to junior high or middle school, with vastly different classes and expectations. Therefore, your ideas for the sixth graduation should emphasize the new maturity that the students will now be expected to display.
Mini High School Graduation
One possible way of showing your students what is going to be expected of them in the seventh grade and to help ease their possible fears is to have a high school graduation-style ceremony for a sixth-grade graduation. The students can wear gowns and caps while being presented with a diploma during the ceremony. It is best to have the students perform this ceremony in small groups at a time to minimize boredom and fidgeting.
Break With the Past
Another way to get the children to realize that the sixth-grade graduation is vastly different from their fifth-grade graduation is to have a visible break with the past. Have the students turn in their ID cards and any elementary-specific items to their teachers and get a diploma in return. This way the children will accept that they are no longer in the elementary school system.
Build them Up with Theme Graduation
A way to get the students to accept their new responsibilities is to use a theme party that revolves around additional power -- for example, a knighting ceremony. Have the students make paper armor and helmets and have the teacher "knight" them with a Nerf sword. This can help relax the students by making the graduation into more of a party atmosphere.
Constantly Reinforce the Students' Self-Esteem
No matter what graduation idea you go with, constantly reinforce the students' self-esteem while at the same time making it clear they have to move on. Many students will have friends who have gone onto the seventh grade and junior high already, so they will have heard some horror stories. Make it clear to them that it is not that bad and that everybody makes it through seventh grade.