The Brave Astonishing Marvelous Dazzling Outstanding Spectacular Invincible (and Hungry) Rubberband Boy

Ohrno Elementary's 5th grade class heads to the local aquarium, where John and Dave are intent on reuniting the school's prize-winning rainbow fish with its friends. When the class returns after John's shenanigans get the school permanently barred, the boys find the school empty. What dastardly evil is afoot? More importantly, can John and Dave stop it without Rubberband Boy's spectacular powers?