Conciseness is good. However, you need to say something of substance. If you want to extremely concise, you can do something like...
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MountainHikerI have a strong record of academic achievement as shown by ...(list them...you can even use a colon if you like). And now, tie in your achievements with your current studies and ultimate career objective.
EvernightI think this is not the best option for me because it would be hard to make this list impressive enough. Yes, I study a lot, and yes, I have some achievements. But yet I don't have too many serious awards or publications. There are things I didn't mention in the original letter, for example, I also occasionally give lessons on programming to high school students,