You don't want there to be good schools that some people can get into and and garbage schools for everyone else. What you need is a high minimum standard that every last school in the nation has to adhere to and it shouldn't be possible to graduate from any of them without being able to read at grade level.
The way it works now is that 20% of the bottom students eat up 80% of a teacher’s time and resources. I’m not saying it’s a bad thing depending on what your goals are. What I am saying is that you can’t have everything. You have to choose. This system this comment describes and the system your comment below describes cannot coexist.
Whether you want that or not depends on what you're trying to achieve. China has pursued basically the approach you're talking about: focusing on key province to advance them to the cutting edge. The last time China participated international high-school testing, they published scores only four Beijing and three other wealthy provinces: https://www.milkenreview.org/articles/are-chinas-students-re.... And those scores were spectacular! Clearly that approach has some merit if your concern is competing with other countries rather than domestic equity.