I would say there is very little or no correlation between marks secured in board examination/entrance exam and success in the professional life.
There is a huge amount of research which shows that the language skills are the best predictor of being a successful professional, and that is why the entire world considers these skills as amongst the most important parameter for both under-graduate as well as post-graduate admissions. But India does not.
Further, there is no transparency and I doubt if the papers are even checked properly. No matter how diligently an examiner checks, he cannot check more than 40 papers of 100 marks each in a day- different handwriting, writing styles, presentation and what not. Especially in a subject like English where the questions are open ended - we cannot quantify them mechanically like a clerical job. And these guys check 11 lakh papers.
I was very shocked to see my results.I got in 80s but scored very very low in Maths(I felt like falling from the 100th floor!). I do not know what was wrong, since I was expecting a perfect 100 this time.
I got 93 in English. But the thing worrying me is that a less deserving student got 96. Even more, a student who has failed in 3 subjects and cannot speak a line nor has written anything in the question paper scored 71 in English.