Keep track of every test score
Yes, there is some wisdom in the saying that ignorance is bliss, but trust that report card grades are stressful enough, without the feeling that you got thrown a curve ball.
There are certain habits that the smart students have and one of them is that they keep track of the grade every quiz, paper, test they get. In high school I watched my best friend write down every grade she got in her student planner. I asked her why and she said that she liked knowing how she was doing in school and what she would have to get on an upcoming test to keep up her grades. Soon I started doing it too. It made life easier in the long run because I knew how I was doing and if I slipped up on a quiz or a test and I knew exactly what I needed to get on the next one to turn around my grade. It sounds slightly obvious, but having a target in sight made it easier to hit it.