Eight Grade Graduation Dance Party

My son is moving up to high school too (this August).
I think your idea to get together with some other parents is great - teamwork planning, cost sharing, and you know the kids want to hang with each other instead of us anyway. Here are some things that might be fun and not so expensive either:

1. Blast from the past portion of the night: Have the parents bring in kindergarten pictures of each of the kids and set them up on a poster board in the banquet hall (you could use these as place cards if you have them sitting at assigned tables). Make an archway for a place to take photos that has the name of the middle school with a big X through it on one side and the name of the high school on the other. Throughout the night anyone who wants to take a photo there will have a nice memento. Email the photos to those who sign up so they can have them printed or set up a photo print station - easy to do with a digital camera & camera printer if you or someone has one - if you have it in a banquet hall they might even be able to set one up for you).
2. The Future: Choose a theme that represents the future. A look ahead perhaps: Space is always a good one: Mock Vacation Posters that say, "Take a Holiday in Venus" or "Mars Dude Ranch", etc... Real Estate posters too, "Land available on Pluto - Lots going fast!" Posters that advertise outrageous and funny future costs like, "Sale on Wonder Bread this week, $10.00". "Buy your wireless house today" "Used flying car sales" etc... Environmentally hopeful posters could talk about clean air cars...
3. Decorate the room to look like the inside of a Space Station. Space themes can be made with the help of backdrops. Spray paint some sheets with black or deep navy paint and then add sparkle for stars. Add 3 dimensional stars, a milky way, black hole, etc. Fog machine could be planetary gasses, planetary ground cover etc. Any surface can be covered with that shiny silver "stuff" at home centers that is light weight and comes in a roll. A 20 inch x 50 foot roll of corregated aluminum goes for about $35.00 but it cuts really easy and can be duck taped to just about any surface (at least temporarily). A little shine goes a long way.
4. Fun Stuff: Create mock newspapers of the future, highlighting the achievements of the kids (one newspaper could cover them all & then make as many copies as you need to give to each graduate to take home). Have the parents provide something their kids excel in and then elaborate. Nobel Peace Prize 2030 goes to... NASA Astrophysicist so and so develops... , Famous Actress so and so has just won her/his tenth Academy Award, and so on. Just make sure each kid is mentioned!!
5. Hand out autograph books or they can bring their year books so everyone can sign, or have themed stationery and "light up" pens on the tables for everyone to use that night. Disposable cameras are also good on tables and keeps them busy!
6. Food: Serve beverages out of neon plastic cups from a "fog-induced" buffet table and make up names of the foods on the table with signs from what planet they come from. "Hot & Spicy Mercury Rising Salsa", etc.
Hope you have fun with whatever you do!
Terri