Not sure if this helps, but this is what i used to do during my college days..
When ever i sit to study i make this list before each exam.
1. Make a list a all possible excuses for why you get low marks (or flunked) each subject.
2. Against each line, put down a worst case scenario of your parents reaction.
3. Below that list out all the possible ways that the low % would impact you. (loss of pocket money, loss of internet/ computer privilages, stright curfew deadlines, loss of any sort of digital content - micro level SOPA
, your friends peers doing better than you etc etc..) hope you get the idea
4. Now make another list which shows the exact opposite list and how getting a good score would impact you..
5. Make both this in really neat writing or print it out and display it where you can look at it everyday (preferable if your parents can see it too.. gives them a heads up of whats to come)
Each day when you look at it, you will get a major confidence boost and automatically sit to study..
PS - preferably do this activity before the exams. In my experience doing this activity after your exam results are out does not yield the aforementioned confidence boost.
PPS - i still do this in my work all the time, except instead of using crayons and paper - i have to prepare a ppt called win/loss analysis.