You could have an auction for the 6 point slots, with the proceeds being divided and distributed to the group.
So, a 20 person class has 2 6pt slots. You take the bids and collect and hold the money. Grades are announced and then you hand out the money or give it back to the original bidders in case of betrayal. The spoiler is basically denying the points and cash to everyone. I get the feeling the identity of the spoiler would be found, if for no other reason all the innocent folks showing their papers. I hope the spoiler is graduating and not coming back because that type of crap is remembered.