Doll on Doll - S2-E5
Other mistake: When Chucky leans over and vomits at the start of the episode, you can hear a vomiting sound effect, but at the bottom of frame, Chucky's mouth dips into view a few times and you can see there's no vomit coming out.
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