It turns out jartboy was an objector, he wanted to help the other children and stop the abuse. That is why Bill put a jart in his skull, but not just to change his mind, it was also to show him something. After the boy went to the hospital and told the nurses and doctors exactly what happened and what was going on, they blamed it on his head injury and told him it was all delusions. When he was well enough to leave the hospital he went back to the Oedings, and that is when Bill made him remove his finger tip.
Gramps said they almost had him turned around but he got fixated on a girl he couldnt have and said if they couldnt give him that girl he wasnt interested in rebellion.
*there was no way the Oedings could be guilty of anything because Bill and some of the girls knew where the priest put the body of the girl who dissapeared. The reason Bill wanted my wristbone was because the Priest wouldnt let him take one from the girl's remains in the shed*