I know I am preaching to the choir, but I need you to do some convincing. Several times over the past week, my beliefs on cushy running shoes have been reaffirmed. Those pillows that some wear under their heels do nothing to stabilize during lifting, jumping and sprinting. After all, you wouldn't wear dress shoes to CrossFit (although they might be better suited than some of these shoes), then why would we wear "running" shoes. And, while these definitely don't help us hit our max potential, my concern is that they might be tweaking the knees in the process. Try this; during the lifting portion of the class, have them take off their Nike Airs and see if they don't become more stable and their squat doesn't improve a little.
100 m sprint
10 Pwr cleans (145/110)