Rex Zero, the Great Pretender — Tim Wynne-Jones

Rex Zero's family is moving, again, this time to a different school district, and his old friends will probably forget he even exists. What's more, a trio of bullies is out to get him. Rex's wild and funny adventures continue as he stumbles into seventh grade, pretending to be someone he's not, and using his overactive imagination to resolve one of life's most vexing problems: just when everything is going well, why does it have to change?