Once upon a time, there was a good hearted teacher who truly cared about his students' success. But he was troubled because one half of his class was failing while the other half was getting an A.
So he decided to do an experiment. He took one grade away from the A students and gave it to the failing students to bring them up to a D.
After a few weeks, he noticed that not only are the failing students back down to an F, but the B students have dropped to C+ students.
So he tried his experiment again. The C+ students were now C students and the failing students were brought back up to a D.
After another few weeks, he was devastated to learn that every single student in his class was failing.
So he pulled his most brightest student aside and said to him "What happened to you? You were always my best student. You always completed your homework and got perfect scores on your tests. What went wrong?"
The student replied "Why should I spend hours after school doing your homework assignments and studying when I'm only gonna get punished for it while the lazy students who watch MTV and play their video games will get rewarded?".