I just read the funniest book and I am positive your third through sixth grader will be rolling on the ground when he/she reads it, too!
Author Jon Scieszka is not only the first National Ambassador for Young People's Literature but he truly understands why boys in particular are reluctant readers. In his autobiography"Knucklehead", Mr. Scieszka relates what it was like growing up as one of six brothers. Some of the stunts they pulled will have you laughing so hard, you'll cry! This is my number one pick for third through sixth graders.
My next choice is "Barnaby Grimes: The Curse of the Night Wolf" by Paul Stewart and Chris Riddell. The authors of The Edge Chronicles series are back with a story about Barnaby Grimes, a messenger (or tick-tock boy as they were called) in old London. Barnaby's friend Old Benjamin is missing, his favorite chair found broken and bloody in the street. Reports of attacks by huge wolves circulate throught Barnaby's favorite haunts. When Barnaby is attacked and begins to investigate, he finds links to Dr. Callwallder and his miraculous new tonic. As the flap on the cover says "A gloriously macabre tale...packed with intrigue, horror and fantastic illustrations." Werewolves, anyone?
Those toys from "Toys Go Out" are back again in "Toy Dance Party" by Emily Jenkins. Lumphy the stuffed buffalo, plush blue StingRay, and hopefully round Plastic the ball are depressed. Honey, their owner, has gone on vacation and left them at home, taking the detested Barbies instead. Honey is getting older and finding new interests and, as the toys feel unloved, they, too, expand their horizons by visiting other areas of the house and finally noticing other toys that they previously dismissed. Wonderful book for your third through fifth graders. By the way, there are obscure references in this book to "The Tale of Despereaux" by Kate DiCamillo, another excellent book for this age group. Try both!
"The Youngest Templar: Keeper of the Grail" by Michael P. Spradlin is the tale of Tristan, an orphan raised by monks, who accepts the invitation by Sir Thomas, Knight of the Templar, to become his squire on a trek to the Holy Land. Tristan runs afoul of Sir Hugh, another knight who seems to know more about Tristan than Tristan does himself. Between avoiding Sir Hugh's cruelty, outrunning the Hashsashins and protecting an important package entrusted to him by Sir Thomas, Tristan and his friends struggle their way from one adventure to the other. If your fifth and sixth graders showed interest in "The DaVinci Code", they will revel in this book.