OK I found it.
"Rachel must use the paddle on Chloe's bare bottom" - You don't have to steal the homework, just occupy Chloe whenever she's working. Rachel should be in a negative mood. Rachel doesn't need to tell you to bring Chloe's homework - or maybe she does and that's a message you don't ever deliver to Chloe? I didn't get that message on that day, but I did get that message on previous days and never delivered it to Chloe. Anyways, once Chloe's been distracted, at dinner Rachel will tell her she's getting smacked on the bare ass tonight. Be at the Corridor at 22:00 and you'll hear *smack*. Peek in on Chloe's room and bam. Phew.