Heir of Hope — Eric Johnson

Torn away from the world he knew and told to take what was rightfully his, Tom is transported through time, finding himself safely at home. But home isn't what he thought it to be. Forces out of his control are at work, his seventeen-year-old mind is trapped in his eight-year-old body. Even more agonizing it's the first day of third grade! Is there any way he can get out of elementary school to keep his family together?