Hi! I am teaching esl in Taiwan and I work at two different schools. It seems like a good idea to have one scoreboard for the class and we can use peer pressure to get the 'challenging' students to behave. Both of the schools have some policies that make this difficult however.
One of my schools has a rule against teachers using collective punishment. I'm not supposed to keep the whole class during break, even for a minute. I have to work really hard to keep track of individual behaviors and that works fairly well.
The other school I'm working at is a kindergarten and the classes have already been broken up into four different groups named after cute, little animals.
Just wanted to ask more experienced wbters what they would do in this kind of situation.

Use a reward only Scoreboard. Play for fun things they would like to do.

A reward only scoreboard isn't as interesting, is it? It's also kind of hard to find things my 4th and 5th graders would like to do. Some of them are from very rich families and are very spoiled.

What about the kindergarten. WBT seems to emphasize using one scoreboard for the whole class. I like this idea as I can sense the general atmosphere of the room and give a smilie or frownie. It feels a lot different when I have the class broken up into 4 groups.

A rewards only Scoreboard can be just as effective and fun as one with rewards and consequences. Rich or poor will not matter. You are not looking at getting them things. Try playing for five minutes of playing Mind Soccer, or three minutes getting to do an activity they pick. One or two minutes listening to the music they want to listen to. Play to go to lunch two minutes early, or come back from lunch a couple of minutes later than everyone else.

Rich or poor they will play hard for rewards like these, and there are no consequences which should please your administrators.