I've had discussions with the assistant principal about effort versus ability, others, or luck. Several studies show significant percentile gains when effort is reinforced. Unfortunately, many students do not connect effort and achievement, but they can develop this belief.
"[O]ne study found that students who were taught about the relationship between effort and achievement increased their achievement more than students who were taught techniques for time management and comprehension of new material" (Classroom Instruction That Works, p.51).
"Reinforcing effort can help teach students one of the most valuable lessons they can learn--the harder you try, the more successful you are. In addition, providing recognition for attainment of specific goals not only enhances achievement, but it stimulates motivation" (Classroom Instruction That Works, p.59).
I'm going to speak about Rewards in another post. For now, I just want to say that verbal reinforcement is a great incentive. Rather than free passes or extra points or a treat, I need to verbally encourage the students. And, that verbal reinforcement needs to speak of effort.