Don't forget that the perceived value of incentives varies. Tell the kid he'll get a bag of marshmallows and even if he thinks you're a liar he might wait the 15min. However, the kid that once got sick from eating a whole bag of marshmallows might not be so inclined to wait it out. The parallel being that kids who's parents went to college (graduated or not) and didn't move up in the world might not see paying attention in high school to be as valuable because "I'm going to be an electrician/whatever, I'm not going to college, I want to get to work and get paid" You see this in college too "I'm not going to grad school, I'll load up on classes/party it up, graduate and be done, C's get degrees, nobody cares about my transcript once I have the diploma"