Could it be possible to let the negative points for discipline be deducted from the positive points.  Our system works as follows - If you get 50 positive points you get a yellow button, if you get 75 positive points then you get a green button and so forth, then the negative points works like this, if you lose 15 points you get a detention, so for every 15 points you lose you sit detention.  We have the problem now, that some of these children gets a yellow button because they have 50 positive points, but in that same instance they also sit detention.  It would be easier if we could only have one set of points to work with instead of two.