I just finish teaching my second MC safety class of the season. My co-instructors were great and both classes were taught and coached in the manner that should generate success. I believe in the 1st one, 5 of 9 passed and the 2nd one, 3 of 7. Of those who didn't pass, I believe that they all could in pass the riding evalutation in time. I encouraged each to get right back in another classes as soon as possible (which will be easier with the abundance of classes that lack 100% confirmed students).
As an instructor, it's frustrating to focus on the end numbers. At the beginning of the last day of riding, my co instructor was a sub for someone who was sick. I shared and he confirmed early in the day that probably 3 of the 7 would pass. The other four weren't endangering anyone, but they weren't progressing to the point that they would be able to pass the riding evaluation. Most importantly, the would be a danger to themselves and other if they were to go on to the street at this time. The 4 who did not pass learned a tremendous amount both on and off of the motorcycle. They just require more development time than was available on a single class.
So in the end, I am blessed to be part of the program and I enjoy the whole thing. The success rate is a point in time for everyone in the class that in only an immediate gage in the process of become a safe/good motorcyclist.