I can't get over the way he treats Yuu in comparison to Rin (although as a M she loves it). I just want to give her a hug and tell her how a good girl she is...
Loved the sex, but I kinda feel bad for the kid/kids on page 1. They only want to hang out and get to know their cute senpai's, and maybe have a shot, but its to late they are already claimed by their sensei.
...So the reward and punishment, as well as the incentive are relatively similar, with the difference being whether or not he cums in them?
I'd say it's a good system for motivating them, except one is being motivated to get bad grades for the punishment instead of the reward...