Originally Posted by Val
Specifically, why all this focus on achievement (past grades and test scores) as a requirement to get into college?

Simple competition.

There are only a certain number of slots at prestige institutions.

And getting a prestige institution diploma means that you have a chance for a Meaningful and Successful Life(TM) because you will be on a Success Career Track(TM) instead of working at McDonalds and living a life of Despair and Irrelevance(TM).