Revealing mistake: In the final shot of Father Bryce exploding, where we see his head falling back down, it seems to hit and bounce off something that isn't there. Likely it bounced off some sort-of rigging that was painted out digitally.
Revealing mistake: When Father Bryce explodes, the second shot looks incredibly unnatural. Much of the blood and pieces sort of vanish, and the lighting doesn't quite match, revealing it's some sort of added effect.
Revealing mistake: When the doll, Jennifer, gets hit by the truck, you can see pieces of the metal armature and wires sticking out of some of the bits and pieces that were used to make the doll stand up. You can also briefly see that Jennifer goes from looking at the truck to looking forward between cuts, but it goes by quick and is hard to see. Slow motion helps but isn't required.
Answer: They were blamed for the death of Jake's foster brother, which was deemed a terrible accident, and they were sent to the reform school as a punishment. Presumably, when they had to leave the reform school given what happened, they were instead given community service as punishment.
TedStixon