On the contrary I had a different experience of Class X Board Exams. I got 100 in Social Science despite the fact I had NOT written as per the answer key. I had written answers with a different insight. I don't think they cut marks for writing extra.
But this year I am in 12th..so let's see...
The main point to be noted is "laziness". Nobody wants to spend a lot of time with an answersheet. I have friends who attempted 40 marks in biology (12th) and got 84. It is possible to get high marks by having a neat and clean paper with lots of good diagrams. They only check for how the paper "feels", not what's actually inside it. When they do check the answers themselves, it's according to the key.
All I can say is that I have been burnt by the state board as well as CBSE and I *know* I wrote much better papers than the marks they awarded me at the time (well, I guess the score still wasn't so bad but it's disheartening to see it happen in 10th as well as 12th knowing that it never happened in 9th or 11th because in those cases I could actually see my paper so that I knew there was nothing wrong with my answers). Knowledge is not rewarded so much as neatness and good diagrams are.
Sheesh.... the current batch is full of nerds... My sis just got her CBSE 12th results... in commerce... The marks (dunno subjects except maths) were 95(english), 95, 98, 98, 99(maths).
In MY time (2 years back) nobody had even HEARD of a 95 in english.... and 3 of her friends got 95 as well.......
IMO the marking systems are getting lenient. Plus, getting 95 doesn't make you a nerd.......
These days I have noticed an avalanche of people getting 95 or so in English, and a lot of them cannot speak a straight sentence properly. The marking system for languages in our country is simply the worst. Ultimately, it is a sad truth that the 12th (and 10th) marks tell almost nothing about the knowledge or aptitude of a student these days.
Even from my own experience I will tell that I was nowhere near as good in Hindi as the marks they gave me.....I never scored more than 55% in a single test since 8th std., and in both 10th and 12th I had marks in the 80s for that subject whereas people much better than me in speaking as well as in college/school test marks had worse marks (you may say that my school teachers may have been biased but I *know* my Hindi wasn't very good, and in some ways, still isn't)
EDIT: I just saw this in the marking scheme for English Core:
CBSE said:
No marks should be deducted for mistakes in usage and grammar, spelling or word limit
If this applies to all other languages, I can see why I scored good marks in Hindi. IMO, even if this applies only to some specific sections, this is unfair to the students who have invested a lot of time in perfecting their language skills. In our school, grammar and spelling errors would mean a 1 or 2 mark deduction out of 10.
Such a system also ensures that people can score 98 or so without knowing proper grammer. In the end we get people who cannot speak worth a damn scoring 90+.....(I'm not saying everyone is like this but I have seen too many to be comfortable with it).
Still, if someone has worked hard to get a good score, I congratulate him/her......my thoughts are just that of a grumpy old man who got burned in years long gone
All the best for entrance exams. 
