This is an excellent question.
When I was at school, they used to teach you explicitly
how to precis.
The ability to write concisely - in exam conditions - is a big ask, I think.
I also hesitate to plough in with advice, which might in fact confuse and misdirect you - really you need to talk to your teacher about this.
Nevertheless, I can offer a couple of ideas.
- When you write an essay for your teacher, go back through it and - before you submit it - cut out all the extraneous stuff, e.g. all those 'In my opinion', 'Therefore, taking all these factors into account', etc. Learn in this way where your style is flowery and cut out the excess.
- Look at your discourse markers; are they too long? Similarly your link sentences?
- Do you start with an introductory paragraph which restates the question and maps out the approach you intent to take? Why not just jump straight in.
- Do you finish with a conclusion which spends a long time simply rehearsing ideas and facts which you have stated already; this is an area which could probably be viciously slimmed down.
- Also you do not need to full out all your 'proving facts' for the examiner - he knows them! In an essay you might say this: 'The proof of this is in the events of 28 june, when a group of Black Hand terrorists plotted and executed the assasination of franz ferdinand as he conducted an inspection-of-the-troops visit to Sarajevo in Bosnia'. But most of that may be unnecessary. In the exam, you could probably get away with: 'the proof of this is in the 28 June assassination'. You only need to mention the details if they directly appertain to the proof.
- Explanation tends to be an area where pupils get very wordy - but I strongly advise you to be careful if you try to cut this. It is one thing to make your explanation more lean - the danger is that you make it more sketchy ... and it is the explanations which get you the marks. Better too wordy than too shallow.
I have been helping to write an English GCSE textbook recently, and came across this lovely idea of the 'three kisses' which - according to Internet expert Harrison Holden - are the three rules of writing a good text:
a. Keep It Straightforward (e.g. not complicated)
b. Keep It Short (e.g. not repetitive)
c. Keep It Structured (e.g. it set out us its information in a sensible order).
I know I know - easier said than done!
As well as in this forum, I write in two environments - I write letters as a local politician to the local newspaper, and I write textbooks.
Both need to be concise. People won't read a letter that it more than 300 words long. A textbook cannot cope with more than 450 word to a page.
SO what I do is I write it full out on the computer at a rush, just shoving in everything.
Then I go back and slim it down.
As a rule of thumb, it takes 3-4 times as long to hone it as it did to write it.
Sometimes whole paragraphs can be cut out; they add nothing to the argument.
At other times it is just a matter of replacing one 3-word adjectival phrase with a single adjective which means the same thing (that is an issue of breadth of vocabulary).
I suggest you do the same thing. When you have written your essay, set yourself an arbitrary word target and then just work on your essay until you get it down - whilst still saying as much.
You will not be able to do this in the exam, of course, but doing so will teach you the way to be concise within your own personal style.
Best of luck