Shelley
Welcome to WBT!! In regards to the scoreboard make the reward for each day, and maybe an accumulation reward for the Fun Friday. In other words, Monday AM if they win, great the reward is two minutes of free time, early relasee, or, what we really want, one of the educational games that we have. Then they loose Monday PM, Tuesday AM, Wednesday AM, and then win again on Wednesday PM. The point of the scoreboard is to get most of the class on board and then worry about the other 10% later. (Read the levels section for this.)
You mention that it's not fair, but when you are bouncing the score back and forth they learn how to do the right thing so that it isn't just three kids doing the right thing...you find the challenging kids doing the right thing and reward them for it quickly. The kids need to feel like they are totally engaged with it and bouncing them back and forth will do this.
Chris