I had students that I knew were smart that I was forced to fail. They would grasp the subjects quickly when I was speaking, they would ask good questions during class...and then they would simply never study or do the homework I assigned them, and then they would do terrible on tests and I'd be stuck having to give them a bad grade. They were smart students, but they didn't want to be there.
I think you need to go a level up. Forget the people that flunked the class. Did the people that get good grades learn anything? Really? Do you think they still know it?
Was learning the point for anyone or any institution involved?