Sheree Fitch 
Pocket Rocks [PDF ebook] 

No matter how hard he tries, Ian Goobie can’t do the things that the other children in his class can do. Then he finds a rock, a rock that fits perfectly into his pocket, a rock that touches all his senses and whisks him away into a whole other world. From then on, as long as he has a rock in his pocket, Ian Goobie can begin to cope with his daily challenges. That is until he stuffs so many rocks in his pockets that his pants fall down right outside in the schoolyard.