over the years i've had several teachers tell the class on the first day that "Other classes tell you you start out with 100 points, HERE, you start with ZERO points and are going to earn every one you get!" i wonder why i learned the most in those classes?
I have had struggling students who worked their butts off only to get a 50. A real 50, not one given to them. They then see that they could have gotten the same grade without even trying and it then becomes extremely difficult to convince them to work hard and keep trying.