That's quite the straw man you've built there.

Nobody is talking about forcing the high achievers to do the teacher's job. The question is how we allocate the fixed amount of educational resources we have. You want us to choose the high achievers so that these early winners can turn that lead into even greater success later. Unstated in your post is what happens to those low achieving students. But it's pretty easy to assume that they're going to be the losers in the winner take all economy.

The other option is to help the low achieving students so that more of them can participate in that winner take all economy. I'm not sure how to argue that this latter option is preferable since it seems so obvious to me that it's the right choice to make.