personal opinion here, but if you have a taller kid jumping STRAIGHT up in the air to retrieve a rebound, I believe it is not over the back...as long as his hands or arms do not come over the opposing player's head, shoulders, etc. In other words, the taller kid would have to go straight up with his entire body which would be kinda hard not to call unless you have a 4 foot tall kid boxing out a 7 foot tall kid, whereas I could see the difference.