Old School by Gordon Korman

From the New York Times bestselling author of The Unteachables comes a hilarious story about a boy who is homeschooled in his grandmother’s retirement community…until he is forced to go to public school.  Dexter Foreman is twelve going on eighty. He has lived at The Pines retirement village with his grandmother since he was six years old, and as a result he gets along better with senior citizens than kids his own age. He's homeschooled by the residents up until the day the county’s truancy officer shows up and announces that Dex has to go to a “real” school, to the local middle school. At school, Dex sticks out like a sore thumb. He dresses like a grandpa (and can be just as cranky). His taste in movies and music is decades out of date. Only a few students—like Gianna Greco, a reporter at the school’s newspaper—find him intriguing. For most, he is either a weirdo or a target. Dexter would do anything to return to his old life at The Pines. But when his wish finally seems to be coming true, his old and new worlds collide in a way that surprises everyone—Dexter most of all.