Scoring marks happens when (1) you have high academic ability (ability to read/understand quickly, and write in exam) and (2) when you study subjects that you understand well as per your passion & talent; e.g. interest in science with high logical ability gets you better marks. If you also have high academic ability, you get still better marks. Some students, even after choosing right degree, do not score good marks if they do not have high academic ability.

But marks do not have much to do in one's long term success. It depends on if you are able to do your work with Speed, Ease and Perfection, even if you are from an ordinary college. Someone may not have high academic ability but may have high potential for some kind of work. If he/she chooses that kind of work, they go far ahead of others. You may get a good rank to get admission to medicine or engg with high academic ability, but you will become a good doctor or engineer, only if you have passion & talent for the same. The only thing that helps with high marks is getting admission to a better college; but college-brand doesn't play much role in one's long-term success & happiness. Best Wishes!