It is best, especially when the graduating classes are large, and each graduate is to be invited, for several parents to share the work and expense of graduation parties, but the good news is, these parties require little supervision and are best held outside. Other options for graduation party locations are: Outdoor pools (where it is warm enough, or indoor pools, where it is not) skating rink rentals, or teen clubs rented for the evening.
Make invitations that look like diplomas, specifying the party location and rules. Then send them to each child in the graduating class. This party should be held on a Friday or Saturday night. Since most graduates have a party planned for the night of the graduation, you should plan to have your party a couple of weeks prior to the actual graduation, if the site is not your home, the location should be booked well in advance.
There is really no need for lavish decorations, but decorations are easily made of confetti, graduation caps cut from black paper, etc. At this age, there is also little need for planning complex activities. Try to get as many as possible to bring yearbooks from kindergarten to the present. Ask well in advance for childhood photos of each classmate, copy, print, and enlarge these. Hang the photos, and provide blanks for everyone to match a name to a photo, and put them in a box with a slot cut into it, and later you can open the boxes to see how many were able to guess which photo belonged to which student. This can be easily accomplished by asking each student to go and stand next to their picture. Another alternative is to create a photo slide presentation, in which each photo is identified.
The only other activity that you will need is plenty of music, preferably loud, plenty of room for dancing, and lots of food and drinks. Choices should be punch, sodas (both diet and regular) bottled water, chips, dip, and hamburgers and hot dogs. These should be set up, so that everyone has access to them whenever they choose, rather than having a set time for eating. Graduation cakes and/or desserts are also appropriate for the last hurrah of this class at their Graduation Party.
Graduation

Graduation parties are extra special with our theme party supplies, decorations, favors and games.
Enjoy
your party!