Need help planning my sons spring/ end of the year party?

I want to do something special for the kids in my son's 3rd grade cl to celebrate a great year. We will have the usual snacks & drinks but I want to reward them for doing well in school. I'm the cl mom and have run out of ideas... we've done bingo, pinatas, scavenger hunts and more... any ideas for something unique and fun for 9 year olds?