Old professors corrupt young innocent chicks. To get the highest grade, they have to give good head.
Disguising it all as private classes at their place, the filthy-minded teachers take the youngest and the sweetest home and trick them into kinky sex. Tempted by better grades, the girls have to suck the wrinkled cocks, lick assholes and offer their virgin butts for penetration. Nobody could have guessed that extra classes could lead to perverted sex acts with their own teachers.