Teachers see what's being missed. Students aren't the only ones who benefit from games in the classroom. Teachers use it to figure out what parts of their course content need adjusting and what topics need to be reviewed. I go back and tweak the course content if there are certain questions that are regularly missed. The combined evidence proves that gameshows increase learning retention and improve the overall attitude about training among students who use the game in class.
Attendance goes up, and people talk about the training long after it's over.