Three problems with this. I suffered all three.
1. He is being put down by a teacher, or another student.
(I used to get bullied in Elementary School, it tortured me enough that i did things my parents would never have thought of. No homework, horrible grades, forging, etc., and worst of all, i acted like i was fine even though i had bruises under my shirt.)
2. You and your wife are not there enough to make a solid bond even if you think you have that "solid" bond.
(My parents aren't usually home and my brother doesn't care. The pain of it kills, literally. I hide the pain, makes it even worse, but i have no choice. My role model [father] isn't anywhere to be found, so i bury it deep and keep moving forward.)
3. You beating him, or yelling, any over negative action, it just isn't the answer.
(It doesn't work, period. It made me more aggressive, careless, stupid, and more depressed.)
Be there for him, it's a long and harmful road. If it keeps going, he's going to go one of two ways, keep going with it, or end it (Literally take his life).