For starters, I appreciate that you're asking this question. It shows that you are among the rare breed that deeply cares about teaching and what the students learn. Because you do, I'll give you my opinion and some cases that prove my point.
I'm a student, and my honest opinion is that you need to stop weighing so much of the class on the test and focus more on growth. The biggest problem in today's schooling systems is that educators focus so much on the numeric portion(grading) of schooling that we often forget about the main goal of grading, which is to measure the progress a student makes and to know if a student reached a certain level of competence.
Many students like myself want to focus more on learning than exams, but we often have to place so much emphasis on the grade because that's what we need to get in and stay in college, get and keep scholarships, get a good first job, and have a good social standing among a lot of people(nobody wants to seem like a nobody). This is especially true for jobs. With the job market getting ever more competitive every year, we need those grades to have a more secure life.
You see why we only learn to the test now?
There's a solution you can enact in your class however. When you have the time read the book Great By Choice & Good to Great. I cant remember which one of the two books said it (I think Good To Great), but by enforcing constant growth that isn't too fast or too slow and using fun as a driving factor within your classroom while only having test to measure the progress (not worth any points), you'll get better results than just teaching to the curriculum. This is because each student will eventually have a sense of confidence in what they're doing. By the end you'll have better students. I can almost promise that the students will worry more about learning.
In the book Good to Great the author interviewed a track coach that helped her students reach Nationals within 3 years. Before they never even reached state. When the author's team asked what her secret was, she said that it was that she boosted the confidence each student had by having them run consistently everyday for fun, no matter the conditions;everyday constantly growing by a certain amount each time. She was never too critical when a person wasn't as good as the and others, she simplily said "It's okay as long as you get better next time, " and she pushed them to do so. When the students reached a certain confidence, they all looked at the Nationals and said "I think that we can win Nationals." She said, "Okay, let's do it" and all did. Sure enough, the team not only won nationals, they had more people sign up for the team.
So how do you do this in the classroom?
State it simply, "It doesn't matter if you do good or bad on exams, if you don't improve constantly as time progress, you'd miss the point of the class and you wont get a good grade." That's how artist teach their classes, at that works out very well. That way a person will grow considerably from your class on and the pressure will be taken off of exam grades and more on the growth from the beginning at the class. Also, try making the smartest person in your class help out everybody else for an extra points. Everything will be balanced by the end.
I totally forgot to add that by showing a lot more care towards the students you instantly get better results. I use this second example a lot.
One of my professors used to tell me the story of his educational childhood. He grew up in an unknown town, is dyslexic, and his single mom had 3 boys and a 5th grade education (extremely horrible in thing in the 50s and 60s). By no means should he be successful in the educational world. All odds were against him. What steered him straight on to graduating in Electrical Engineering on the deans list at Michigan State University and attending grad school at MIT was that a teacher in second grade sat down with his mom and said, "Your son has a reading problem, but we'll work together and solve this problem and bring out his best potential" -- and of course she did --, he instantly became more attached to school and learning. It meant something more to him. He felt less like a number and more like an individual.
Sit down and work with each of the students a lot more. Basically force a 10 - 20 office hour and work with them. They'll feel like you care, even while you might be tough on them and you'll notice every single one of them will do better.
If you have a big class, show care to a small group of students then set the expectation for them to do the exact same.