The Sheriff's In Town: An Idea for Managing Kids in Large Groups

One of my daily duties is supervising lunch for one of our grade-levels.  Earlier in the year, I must admit, I was at my wits-end trying to figure out how to turn what could potentially be a fairly chaotic, unstructured time into an organized, pleasurable, relaxing time with friends.  There are two or three other staff members who have this duty at the same time that I do and we have tried several things to take it down a notch and make it as structured as lunch time can be without taking all of the fun out of it.  One thing that we implemented recently that seems to be working is The Sheriff.
For several months, I found myself trying to control about 120 little bodies when it was time to leave the cafeteria. Many of them could handle this just fine but there were enough runners, screamers, chasers, and ninjas that it took a lot of effort on my part to keep everyone in a line without anyone slipping and falling or playing too rough and hurting someone else.  It occurred to me one day that I was doing more work than I should be.  There were enough students in that line who could model good behavior, I didn't need to be doing all of the work myself.  I remembered I had cut out some golden, glittery stars for a project earlier in the year and I decided to put them to good use.  I chose a Sheriff from each class and asked them to patrol their line.  If a  student is talking, they get a warning, and then The Sheriff tells me and the rule-breaker gets a consequence.  Though it isn't perfect, it's been working and I'm hoping we can keep using it for the rest of the school year.
There are a couple of reasons why I think it works.  First of all, the consequence is a whopper.  Most of the time, it's lunch by yourself the next day, something I call Lonely Lunch.  If you earn Lonely Lunch, you're still in the cafeteria, you just have to sit at a table where the students are more spread out and they aren't allowed to talk. I know it might sound mean but it is a deterrent.  Secondly, kids know if they are quiet, they might get to be The Sheriff the next day.  Everyone wants to be The Sheriff.  Who doesn't want to be the one left in charge while the teacher is away? Most students will work to earn a reward that involves authority, recognition, and tattling.
But that has also created a little bit of a problem. I've had to be careful of the tattling. One has to know the students well enough to know if a Sheriff is just naming students they aren't particularly fond of.  I also have to be leery of Sheriff's who ignore their friends when they are breaking the rules.
Kids like novelty, they like props, and they like being in charge.  So far, this is working. Hopefully, it won't wear off and we'll be able to see it through the end of the year.  What ideas do you have for managing students in large numbers?

I bought a sheet of pre-glittered gold paper at Michael's for about $2 and cut the stars out from that. Pretty simple!