I remember my sisters year did a think they called "The Challenge" they all had studies which there were about 4 people in each, they received a random letter under the door explaining that there were various objects around the school which the challenge was to steel them,
different things had different points values. (Each study was to only have one of each item and the final score went to the study not individuals)
eg .A fork from the dining room, 1 point,
a room number sign 2 points,
etc.etc.etc.
They were to cut the green tick from the bottom of the page out and place in in the right hand corner of the door with the number of people taking part, (some people didnt want to join in and some didnt have as many in the study)
It was going really well until it got out of hand by the bottom of the list as the items included the head teachers Cloak (the graduation ones which posh school teachers wear),
the honour board with all the head boys/girls of past years on (this got really out of hand when the person who stole it had it stolen from his car, they didnt then know who had it and they were all threatened with expulsion only to be allowed back for the final exams.
So anyway if you could do this with some sort of control, you could then give individual scores on each persons yearbook page.