Your mother is crying because unfortunately all aprents tend to want the best for their children and they expect us to do outstanding work so that we can have a great future. Perhaps she feels this will affect you in some way and she is worried about you? It could also be that she is embarassed by it and in that case it is more about her than it is about you.
As long as you are ok with failing your last exam that is all that matters. Can you not take it again sometime? If so then explain this to your mother. Explain that it will not stop you from doing what you want to do and overall just put up with it for now. She obviously has some issues of her own and they should pass with time.
I have also failed my final assessment, though I haven't told my parent. I've got chance to resit so "if" I pass this time, I will hopefully be telling my parents the good news.
I say don't worry about it, if your not bothered about 1 exam (who cares right!) just concentrate on others o next time =p
Look Sohami! they way you have put your question, reflects that you are not concerned about your result any more. You do not think that it should have not happened. You do not think you should be thinking of improving in your next exams.
You seem to have lost you touch as a good student or good son. Your father seems to be the person who is the reason behind the attitude like yours.
You do not have to study if you do not want, go on the roads, drive rickshaw or fetch a cart, do not think of your future to be bright. Your mother is crying because she can feel your failure as her own.
There is still time to be on the right track you can do it if you are willing to do it. The boys who get higher ranks in exams do not come from space. They are quite similar to you, but they are determined to achieve their goals unlike you.
So what do you think now, are going to change yourself or not. If yes, then my good wishes are with you. And if not, then what can I say, and then see you on the road driving a taxi or rickshaw may be.